By Ted Alan Stedman

They’re weird, wild and bizarre. Many call them ugly — so ugly that they’re, well, fugly.

Which is part of the reason divers love these denizens of the deep, those mesmerizingly wonderful marine species that would seem utterly alien if they weren’t in fact real.

The undersea world is replete with all things beautiful. So to mix it up, we offer our unsightly picks that add another wow-factor dimension to the diving experience.

Take the challenge to see if you can find these creatures that only a diver could appreciate.

TASSELED ANGLERFISH

Melbourne, Victoria, Australia

To untrained eyes, the tasseled angler (also tasseled frogfish) gets overlooked, dismissed as another algae-covered rock due to the long filamentous appendages that completely envelop its rotund body. Using its superior camo, Rhycherus filamentosus attracts prey by deploying its long dorsal spine tipped with a glowing, bacteria-charged “lure” before inhaling catches with its voluminous mouth.

Bizarre as it is, this tousled creature is exemplary for its resourceful evolutionary adaptations that scientists think occurred between 100 million to 130 million years ago. One of more than 200 anglerfish species, the tasseled is endemic to Australia, particularly the southern states of South Australia, ­Victoria and Tasmania, where temperate waters foster dense kelp beds the species prefers. Sightings are not only common but also convenient. Where ­Mornington Peninsula separates ­Melbourne’s Port Phillip Bay from the roily Bass Strait, shore and boat divers are privy to tasseleds at Blairgowrie Pier. Considered the best pier/muck dive on the peninsula, the kelp-shrouded site is a virtual marine lab of sponges, soft corals, nudibranchs — and the obscure stealthy predator that’s fished these waters for millennia.

>When to Go Anglerfish are present throughout the year. Strong tidal currents make Blairgowrie Pier a slack-water dive. Consult tidal charts and confer with a dive operator beforehand.

>Operator Aquability (aquability.com​.au) is a full-service dive shop located south of Melbourne in the suburb of Mentone, and offers guided dives throughout Port Phillip Bay.

>Price Tag Boat dives start at $56. Air fills and equipment rentals are available for independent shore divers.

STARGAZER

Moalboal, Visayan Sea, Philippines

With its toothy upturned maw, oversize head and bulbous wild eyes aiming skyward, the stargazer looks otherworldly — like an alien apparition worthy of a Steven Spielberg flick. Upward of 50 species comprise this Uranoscopidae family of perciform fish distinguished by eyes on top of their head. Found worldwide in tropical and temperate waters, this strange critter is a benthic bottom dweller that buries itself in the sand to ambush prey that stray overhead. While most stargazer species hover in the 12-inch range, the giant stargazer (Kathetostoma giganteum) found in the waters of New Zealand can post a gargantuan 3-foot length. Add to its E.T. appearance the fact that it’s venomous, with two large poison spines that can also deliver electric shocks up to 50 volts, and the stargazer stands apart from nearly anything that slinks, swims or squiggles in the ocean.

In the Philippine dive mecca of Moalboal, stargazers are standard protocol for muck-diving sites inside the bay, says Chris White of Turtle Bay Dive Resort.

“We like doing this shallow muck dive at night when your flashlight suddenly illuminates this scary-face fish buried in the sand and staring up at you,” he says.

>When to Go  Stargazers are observed year-round. Peak diving months are November and December, and continue to June.

>Operator  Turtle Bay Dive Resort (turtlebaydiveresort.com), located in Moalboal on the island province of Cebu, offers daily dives in Moalboal Bay.

>Price Tag Two-tank guided boat dives run $65. Through September, seven nights, all meals, airport transfers plus 10 guided boat dives start at $859 per person.

RED-LIPPED BATFISH

Galapagos Islands, Eastern Pacific

You might think of the red-lipped ­batfish as the sad clown of the underwater world. Its frowning, pouty red lips look as if the creature went gonzo with makeup to compensate for its homely hatchet face. And there’s the rhinolike protrusion housing its illicium, the fleshy extension that enables it to “fish” for prey, as do other anglerfish. Did we mention it’s a terrible swimmer? Together with its flat, batlike body and propensity to “walk” the ocean floor with pectoral fins, it’s no wonder Mother Nature Network dubs them among “13 of the ugliest animals on the planet.”

Yet Ogcocephalus darwini is a ­fascinating deepwater species found only in the Galapagos, and prize ­sightings are for the taking, says ­live-aboard operator Peter Hughes.

“We visit three sites where they’re nearly guaranteed, like Punta Vincente Roca. This is a deep, dark, beautiful dive, and the red-lipped batfish is nearly always found on the sand at a depth of 75 feet,” he says.

Hughes advises divers to get low on the sand and approach them slowly or they’ll spook and swim away — awkwardly.

>When to Go  Batfish are sighted year-round. Most divers prefer the “Garua” cold/dry season from July to November, when whale sharks congregate.

>Operator Peter Hughes’ DivEncounters operates the M/V Galapagos Sky (galapagossky​.com), a 100-foot luxury live-aboard that visits all the top dive sites year-round, including reliable batfish sites.

>Price Tag Seven-night cruises with four dives per day and three land excursions begin at $5,494 per person.

REEF STONEFISH

Cairns, Great Barrier Reef, Australia

To our anthropomorphic sensibilities, Synanceia verrucosa — aka reef stonefish — is as fugly as they come. Resembling an encrusted rock or lumpy coral, it can have splotchy patches of yellow, brown, orange, gray and red, which add to its superb camouflage — and ugliness. But there’s another aspect of its ­macabre physiology that puts it on our list: its danger to humans. Not only are reef stonefish venomous and the most widespread species of the stonefish family, but it is the world’s most venomous fish. The fleetingly fast carnivorous bottom dweller is armed with 13 ­dorsal-fin spines, each with two venom sacs ­producing an extremely lethal toxin that attacks both the ­cardiovascular and neuromuscular systems. Most recorded deaths involve humans stepping on the creatures in shallow reefs of the ­Indo-Pacific and Red Sea.

Naturally, with this kind of marine mojo, reef stonefish are a much-sought check-off for cautious divers. One of the best reliable havens is along the Great Barrier Reef at Steve’s ­Bommie, where captivating caves, canyons and coral gardens belie the reality that these menacing-yet-mesmerizing creatures are literally underfoot and nearly everywhere.

>When to Go Sightings of stonefish occur year-round. Best viz is from August to December.

>Operator Diving Cairns (divingcairns.com​.au) is located in Cairns, Queensland, gateway to the Great Barrier Reef.

(CNN) -- Bored of diving among the usual coral reefs and tropical fish? Looking for something a little out of the ordinary?

Ever thought about diving in a crack between two continents in some of the clearest water on Earth? Or what about swimming up to an active volcano? Perhaps underwater art is more your thing?

If so, take a look at some of the most unusual, mysterious and awe-inspiring underwater landscapes from around the world.

Continental rift in Iceland

The only place in the world where you can swim between two continents, the Silfra fissure in Iceland's Thingvellier National Park is where the North American and Eurasian tectonic plates meet.

Not only can you dive in a crack in the earth caused by the two continental plates slowly moving away from each other (at an average of 2 cm a year), the waters are so clear that many divers are said to lose all sense of depth and even experience vertigo.

The water's extreme clarity is thanks to year-round cold temperatures of around two to four degrees Celsius and the water's purity. The water originates from a glacier high on Iceland's Hofsjokull Mountain and is filtered through layers of porous lava rock before reaching the national park. Not only is it cold and clear, the water is so pure it is safe enough to drink.

The three sections of the dive include Silfra Hall, the Cathedral and Silfra lagoon.

Mysterious ruins in Japan

A long-lost civilization, the work of aliens or simply a natural wonder? The mysterious underwater ruins of Yonaguni continue to lure the most intrepid of divers.

Located in the Yaeyama Islands off the westernmost point of Japan, the tiny island of Yonaguni is remote and difficult to reach. But it remains popular thanks to the archaeological riddle submerged off its southern coast.

Exactly how the underwater pyramid structure, known as the Yonaguni monument, was formed is still under debate. Some claim the ruins to be evidence of a long lost city, while others are convinced it is a geological phenomenon. There are even a few who believe the site to be the work of architecturally-ambitious aliens.

Whatever its origin, it's an impressive site. Estimated to be between 5,000 and 8,000 years old, the stepped structures -- with smooth platform steps and right angles -- appear as though they were carved out of the rock.

This is not a diving site for beginners, with the ruins located in open waters with high waves and strong currents.

Volcanic action in Indonesia

Want to see a volcano up close without the threat of lava flows and toxic air? If so, the submerged volcano of Banua Wuhu is the place to head.

Located beside the island of Mahangetan, part of the volcanic island chain of Sangihe in Indonesia, Banua Wuha rises more than 400 meters from the sea floor and is less than five meters below the water's surface.

There is no risk from lava -- instead, the underwater volcano releases ribbons of silver bubbles -- sulfur gas -- escaping deep from inside the earth's crust.

"The bubbles can burn your fingers if you're not careful," said Roman Szalay, managing director of Ocean Rover Cruises, which charters one of the few boats that makes the journey to the volcano.

"If you bring (the gas) up in a bottle to the surface it smells horrible, but if the bubbles come up to the surface it smells like nothing," he added.

The further you descend, the volcano's barren sulfur-covered rocks give way to coral reefs and an extraordinary display of marine life, including huge barrel sponges, black tipped reef sharks and schools of neon fusiliers.

"If the sky is cloudy and the sun is not bright, the atmosphere is quite mystic" said Szalay, "Sometime you can also hear the roaring of the volcano."

Underwater art in Mexico

Want a bit of culture on your next dive? Then try the tropical blue waters of Cancun, Mexico where you will find the Museum of Underwater Modern Art.

Consisting of more than 403 permanent life-sized sculptures, the art-filled sea-bed is one of the largest artificial reef attractions in the world.

The work of British sculptor and scuba diver Jason deCaires Taylor, each sculpture is individually cast and made using a special cement mix to encourage coral growth.

"It's incredibly interesting working underwater," said deCaires Taylor. "The colors are different, the light patterns are very different, the atmosphere and mood is otherworldly.

"The piece takes on a very different tone underwater -- it has a lost feel to it and brings up all these questions that you wouldn't have on land," he continued.

Underwater cemetery in the U.S.

A little over five kilometers off the coast of Miami, Florida, is an altogether different, and slightly creepy, diving experience -- an artificial reef that doubles as a cemetery.

The Neptune Memorial Reef, with its tagline "creating life after life," is a man-made reef, built to encourage the growth of marine life while creating "the ultimate 'Green Burial' opportunity."

People who choose the reef as their final resting place are first cremated. Their remains are then mixed with non-porous cement, sand and water, and molded into a stone shape of their choosing, such as a shell or starfish. The stone is then added to the reef by scuba divers.

The first phase of the memorial has been built in the style of a "classical re-creation of the Lost City." Relatives of the deceased, curious scuba-divers and marine biologists are among those who dive among the coral-encrusted arches and statues of lions that line the sea floor.

When completed, the memorial will cover have the capacity to hold the cremated remains of around 100,000 people.

New underwater footage posted online Friday is believed to be the world’s first video showing a pod of killer whales hunting and killing a tiger shark.

According to Barcroft TV, the video was captured off the coast of Costa Rica by photographer Caroline Power on September 8th.

The wildlife video shows three killer whales work in unison to force the shark toward the surface, before they bite off its fins. Ultimately, one of the killer whales delivers a final blow to the shark.

 http://www.youtube.com/watch?v=uqimOYOQjJ8&feature=player_embedded

Since 2010, Scuba Diver Life has amassed over 1 million Facebook fans and now has roughly 1 million monthly website visitors. We’re excited about our past and current growth, and have spent the last year working on a new mobile- and tablet-optimized website. Along with these changes, we’ve just released a new mobile app, which will deliver rich media content to subscribers on a monthly basis. 

Visit the new site at ScubaDiverLife.com

Download the new Mobile App : CLICK HERE 

Highlights of the new website include: 

Dive Map: 

The dive map on ScubaDiverLife.com offers users a new and unique way to search for content based on location. It’s now even easier to research where you want to go and check out available diving adventures before you get there. 

Videos: 

We’ve aggregated all our video posts into one easy-to-navigate section. Now it’s even easier to discover cool scuba diving and ocean conservation videos!

Galleries: 

A picture tells a thousand words, so we’ve also aggregated all of our stunning galleries so you can visually explore new dive destinations and see what’s happening in our oceans around the world. 

Mobile App:  

Along with launching our new website, we’ve just released the latest (and greatest) version of our mobile application, which offers exclusive Scuba Diver Life content to subscribers. We’ve worked very hard to give them a rich media experience on their mobile devices, a first for the dive industry. We’ll continue to add even more functionality and ways for users to engage. 

We want to give big thanks to everyone in the industry who has been supportive over the past four years. We at Scuba Diver Life are excited to share these new platforms with divers worldwide and look forward to helping divers discover even more about our oceans every day. 

Visit the new site at ScubaDiverLife.com

Download the new Mobile App : CLICK HERE 

The Bald Cypress forest was buried under ocean sediments, protected in an oxygen-free environment for more than 50,000 years, but was likely uncovered by Hurricane Katrina in 2005, said Ben Raines, one of the first divers to explore the underwater forest and the executive director of the nonprofit Weeks Bay Foundation, which researches estuaries.

The forest contains trees so well-preserved that when they are cut, they still smell like fresh Cypress sap, Raines said.

When asked why he decided to dive deeper than any person had before, Ahmed Gabr, 41, told the media that he was hoping to prove that humans could survive the conditions of deep sea immersion, according to Guinness World Records.

Diving off the coast of Dahab, Egypt, Gabr reached a depth of 1,090 feet 4 inches (332.35 meters). The previous record holder for the deepest scuba dive, Nuno Gomes of South Africa, also dove off the coast of Dahab, in 2005, reaching a depth of 1,044 feet (318.21 m).

Exactly 150 years later, a new 3D map of the USS Hatteras has been released that shows what the remains of the warship look like. The Hatteras rests on the ocean floor about 20 miles (32 kilometers) off Galveston, Texas, according to a release from the National Oceanographic and Atmospheric Administration, which helped to sponsor the expedition to map the shipwreck.

The Hatteras was sunk in a battle with the Confederate raider CSS Alabama, and was the only Union warship sunk in combat in the Gulf of Mexico during the Civil War.

In the image above, the 3D sonar view of the USS Hatteras is from the vessel's port (left) side. More than half the hull lays buried in sediment. The curved tooth-like outline to the right is the remains of the stern and rudder.

 Credit: NOAA's Office of National Marine Sanctuaries/ExploreOcean et al 

The Silfra fissure, is known as one of the top dive sites in the world two main reasons.

First, the Silfra fissure is actually a crack between the North American and Eurasian continents, meaning that you dive or snorkel right where the continental plates meet and drift apart about 2cm per year.

Silfra is the only place where one can dive or snorkel directly in the crack between two continental plates.

Secondly, the underwater visibility in the Silfra fissure is over 100 meters, which creates an underwater experience that will rarely, if ever, be surpassed. The reasons for this astounding water clarity are twofold: the water is cold (2°C – 4°C year round ) as it is glacial water from the nearby Langjökull and this water is filtered through porous underground lava for 30-100 years until it reaches the north end of Thingvellir lake, seeping out from underground wells. The Silfra water is as pristine as water can get and you can drink it at anytime during your dive or snorkel.

The Silfra fissure consists of four sections: Silfra Big Crack, Silfra Hall, Silfra Cathedral, and Silfra Lagoon.  We plan our dives and snorkel swims so that we are able to see all Silfra sections in every Diving Silfra Day Tour and our Silfra Snorkeling Tour.  We enter the water from a platform with steps leading down.  If you are diving, the maximum depth of the your dive in Silfra will be 18 meters, but the average depth of the dive is between 7 and 12 meters.

Although Thingvellir Lake has an abundance of fish species and trout fishing is very popular in the lake, the fish usually do not venture far into the Silfra fissure.  The marine life in Silfra consists mostly of bright green “troll hair” and different types of algae that provide a colorscape unlike anything that occurs naturally above the surface.

The National Park Thingvellir has been declared a UNESCO WORLD HERITAGE SITE both for its cultural and historical significance as well as natural and geological uniqueness.  It is well worth it to join our Golden Circle Day Tour to further explore Thingvellir on land.  Moreover, if you have friends or family accompanying you on your tour but do not wish to get in the water themselves, the area around Silfra is full of lovely walking trails that lead through this fascinating place.

"Nobody understands the allure of the sea more than the U.S. Coast Guard, but we also see the tragic results when people underestimate the hazards. The adventure and thrill of diving are appealing to many, but the ocean is an unforgiving environment — and even less forgiving to those who recreate beneath the surface."

— Rear Adm. Karl Schultz, commander of the 11th Coast Guard District

Recreational diving is by and large a safe activity, but when accidents occur the outcomes are often frightening and can be fatal. The beautiful blue world below can quickly become hostile for divers who lack adequate training, are in poor physical condition, use improperly maintained equipment or are otherwise unprepared.

Although the U.S. Coast Guard does not have regulatory authority over recreational diving as it does for recreational and commercial boating, Coast Guard search-and-rescue crews are frequently called on to assist when divers are lost or in trouble. In the aftermath of a dive injury or death, the Coast Guard marine casualty investigators work with other public health and safety organizations to identify what went wrong and evaluate how to prevent future accidents.

In 2009 the Coast Guard began to forge strong partnerships with the San Diego Lifeguard Services, the San Diego Harbor Police, the San Diego County Medical Examiner's Office, the University of California San Diego Health System and the Scripps Institution of Oceanography to analyze dive incidents. The committee formed by these groups produced six recommendations based on a comprehensive review of diver fatalities in the San Diego area. The committee encourages divers everywhere to ask themselves the following questions:

1. Is your training adequate for the current and predicted conditions? Will you respect the limitations created by the conditions and stop diving when conditions change or exceed your personal limits?All the normal hazards of water sports are magnified for those who spend time beneath the surface. Strong currents can occur at any time of year. Cold water temperatures, limited air supply, reliance on equipment for survival and the lack of underwater rescue capabilities make it essential that divers are fully aware of their limits and prepared for all possible problems.

2. Are you prepared to abandon your weights, inflate your buoyancy compensator and signal for help when in distress?Divers should not be afraid to ditch their weights, end their dives and signal for help at the first signs of distress. Interviews with divers who have experienced distress reveal that many of them did not understand they were in danger because they had not been taught how it would feel; therefore, divers should signal for help if they have any concerns at all.

3. Is your physical fitness adequate for the current and predicted conditions? Have you checked with your primary doctor to ensure that you are in good enough health for intense physical exertion? Diving is a strenuous physical activity involving physiological demands unlike those of any other sport. Many dive fatalities are caused by heart attacks, and the risk is especially great for divers over the age of 45. Divers who have not dived in more than a year should consult with their primary-care physicians before attempting to return to the sport. They should then reassess their abilities with a simple or less-challenging dive.

4. Are you diving with a buddy? Have you reviewed each other's abilities, equipment and plans?In addition to planning, health, physical fitness and awareness of weather and sea conditions, dive-safety experts stress the importance of the buddy system. Divers should never dive alone. They should always have detailed plans (which include times and locations) that they share with someone ashore.

5. Do you feel completely comfortable making this dive?It is essential to prioritize safety and remain realistic about upcoming dives. Any hesitations about any aspect of a dive should be completely resolved prior to commencing the dive. Divers should also clearly understand their experience levels and only attempt to exceed these limits when the conditions are optimal and they are diving with more experienced partners.

6. Do you plan to enter overhead environments? If so, do you have the proper training and equipment, and are you familiar with the necessary procedures?Diving in caves, wrecks or any overhead environments in which the path to the surface is indirect necessitates additional training, equipment and air supply. In overhead environments, prepare yourself for confined spaces, entanglement and disorientation.

According to the Coast Guard's Tactical and Strategic Statistics, in the past four years (2010-2013) the Coast Guard was called for assistance in 63 fatal dive accidents and 55 diving-related injuries. We hope that publishing these safety tips will lead to fewer dive-related tragedies. "The Coast Guard doesn't regulate recreational diving but is generally called in to assist during diving emergencies," Schultz said. "In many of these dive emergencies, injuries and death are preventable. We want everyone who enjoys the water, including divers (whose sport leaves little room for error), to make safety their top priority. We want you to survive your dive."

The problem is, they're not exactly sure what it is they've uncovered.

Out searching for shipwrecks at a secret location between Sweden and Finland, the deep-sea salvage company Ocean Explorer captured an incredible image more than 80 meters below the water's surface.

At first glance, team leader and commercial diver Peter Lindberg joked that his crew had just discovered an unidentified flying object, or UFO.

"I have been doing this for nearly 20 years so I have a seen a few objects on the bottom, but nothing like this," said Lindberg.

"We had been out for nine days and we were quite tired and we were on our way home, but we made a final run with a sonar fish and suddenly this thing turned up," he continued.

Using side-scan sonar, the team found a 60-meter diameter cylinder-shaped object, with a rigid tail 400 meters long.

The imaging technique involves pulling a sonar "towfish" -- that essentially looks sideways underwater - behind a boat, where it creates sound echoes to map the sea floor below.

On another pass over the object, the sonar showed a second disc-like shape 200 meters away.

See also: Quest for Sir Francis Drake's remains

Lindberg's team believe they are too big to have fallen off a ship or be part of a wreck, but it's anyone's guess what could be down there.

"We've heard lots of different kinds of explanations, from George Lucas's spaceship -- the Millennium Falcon -- to 'it's some kind of plug to the inner world,' like it should be hell down there or something.

"But we won't know until we have been down there," said Lindberg.

The Head of Archaeology at Sweden's Maritime Museums, Andreas Olsson, admits he's intrigued by the picture, but remains sceptical about what it could be.

The reliability of one-side scan sonar images is one of his main concerns, making it difficult to determine if the object is a natural geological formation or something different altogether.

"It all depends on the circumstances when you actually tow the [sonar] fish after the boat," he said.

"What are the temperature conditions, the wave conditions, how deep is your fish in relation to the sea bed etcetera and all those parameters also affects what kind of image you have in the end," he explained.

Even Lindberg agrees the image "isn't the best it could be." But his crew are still planning to return to the site in the calmer waters of spring to investigate their find.

It's a risky and expensive business, and not one that always pays off.

British maritime historian, Professor Andrew Lambert, says the costs of recovery are now too high for most.

"If you want to stand in a cold shower tearing up £50 notes, go shipwreck hunting," he said. "Most shipwrecks are rotting away, or carrying dull things -- all the romance has been taken out of it."

It's a problem Lindberg and his team are aware of.

"It's a very difficult industry to be in -- it's money all the time," he confessed. "The best thing it could be, would be 60 meters of gold -- then I would be very happy."

"This thing is very far out, it's really off-shore, so first of all we need a bigger ship... more equipment.. and we have to do bottom sampling, water sampling, to see if it is something poisonous."

But even if the mystery object doesn't contain retrievable treasure the site could still prove to be a gold mine for the Ocean Explorer team, with tourists and private investors paying to see it up-close, in a submarine.

"The object itself is maybe not valuable in the sense of money it can be very interesting whatever it is, historical or a natural anomaly," said Lindberg.

In the North Atlantic, one American salvage company is also hoping to beat the odds.

Using side-scan sonar, the team found a 60-meter diameter cylinder-shaped object, with a rigid tail 400 meters long.

Odyssey Marine Exploration -- a company made up of researchers, scientists, technicians and archaeologists -- have at least 6,300 shipwrecks in their database that they are looking to find.

Their latest discoveries include two British war-time shipwrecks off the coast of Ireland that could be laden with hundreds of tonnes of silver.

Mark Gordon, president of Odyssey, says at least 100 ships on their watch-list are known to have values in excess of $50 million dollars.

"When you think about the fact until the mid 20th century, the only way to transport wealth was on the oceans and a lot of ships were lost, it adds up to a formula where we have billions of dollars worth of interesting and valuable things on the sea floor," he said.

The lure of treasure has lead to an increasing number of discoveries in recent years. But one which doesn't come without its dangers, warns Olsson.

"I think recently we're entering a time of a lot of discoveries," he said of the technological advancements in finding shipwrecks.

"The professional shipwreck discoverers are doing a great effort for cultural heritage management in the long run... what we don't support is the action of actually taking up items and selling them," he said.

Conventional wisdom has long held that corals -- whose calcium-carbonate skeletons form the foundation of coral reefs -- are passive organisms that rely entirely on ocean currents to deliver dissolved substances, such as nutrients and oxygen. But now scientists at MIT and the Weizmann Institute of Science (WIS) in Israel have found that they are far from passive, engineering their environment to sweep water into turbulent patterns that greatly enhance their ability to exchange nutrients and dissolved gases with their environment.

Conventional wisdom has long held that corals -- whose calcium-carbonate skeletons form the foundation of coral reefs -- are passive organisms that rely entirely on ocean currents to deliver dissolved substances, such as nutrients and oxygen. But now scientists at MIT and the Weizmann Institute of Science (WIS) in Israel have found that they are far from passive, engineering their environment to sweep water into turbulent patterns that greatly enhance their ability to exchange nutrients and dissolved gases with their environment.

Usually there’s some sort of payoff to diving in near-freezing conditions — a magnificent wreck perhaps, or a unique geological feature. I wasn’t so lucky. When I first dived in 37-degree water, in a shallow lake outside London, there was nothing. Well, that’s not quite accurate: At one point I think I spotted a traditional British black taxi through the murk. But I couldn’t be sure — with visibility of only 20 feet, it was hard to tell.

It was so cold, I could barely think. This was problematic because I was there to make the open-water dives for my PADI Dry Suit Diver qualification and needed my wits about me. The water temperature at Wray Bury Dive Centre’s 15-acre lake is always on the chilly side — this is England, after all — but 37 degrees was unusual. A cold snap the week before caused the surface of the lake to freeze, though it had begun to melt by the time of my visit.

Taking my first steps into the lake was just about bearable. It was when my hands — protected by only 3 mm of neoprene — touched the water that I got a sense of just how hard this was going to be. But that was nothing compared to the brain freeze that struck as I made my first descent. I’m a confident, experienced diver, not prone to panic, but the feeling of ice-cold water surrounding my head and neck was too much. I motioned desperately to the instructor that I needed to surface, and came up, my breathing shallow and hurried.

He helped me to calm down, and we soon rejoined the rest of the group on a platform at 22 feet to complete the skill tests. That dive, and the follow-up that afternoon, were kept to just 20 minutes’ bottom time due to the cold. Even so, I had such limited feeling in my fingers by the time I came up for the skill tests that basic tasks — like undoing the clips on my BC or disconnecting and reconnecting my dry suit second stage — were enormously challenging. It took several attempts, with a great deal of motivational support from my instructor, to demonstrate the skills successfully.

Writing about the experience today while I’m warm and dry, it’s hard to even conjure that unexpectedly extreme environment. They are still the hardest dives I’ve ever made.

It's true what they say, getting narced is fun — of a certain kind. Similar to drinking way too much, then driving waaay too fast. As in, "Whoa, dude, you almost hit that tree! Hahahaha!"

Which should indicate the downside. Not to sound like your mother here, but nitrogen narcosis is, in fact, drunk diving. Though you hear a lot about decompression illness, getting narced should probably be a bigger worry, at least when you dive below 100 feet. At that depth, nitrogen narcosis becomes more likely than a DCI hit, and when it occurs it is more dangerous because it attacks your most important piece of life-support equipment: your brain. That, not DCI, is the primary reason for the traditional recreational depth limit of 130 feet. But there's good news too: You can manage this risk and still dive safely below 100 feet.

What Is Nitrogen Narcosis?

You probably know the term "rapture of the deep" and have heard stories of divers offering their regs to fish and so on. Inappropriate euphoria and general silliness are the best known symptoms of nitrogen narcosis, though narcosis can also trigger anxiety, even terror. The exact mechanism is not well understood, but it's probably no coincidence that the usual symptoms resemble the early stages of general anesthesia. Compare, for example, the effects of the common dental anesthetic nitrous oxide, called laughing gas. "The same kinds of mechanisms are involved," says Dr. Peter B. Bennett, author of the chapter on inert gas narcosis in Alfred Bove's Diving Medicine. "General anesthesia and nitrogen narcosis both occur when a given anesthetic gas — and I would include nitrogen as one — reaches a certain critical molar concentration." In fact, nitrogen narcosis "may be considered as a state of impending general anesthesia" according to the authors of Diving and Subaquatic Medicine. Not the best mental state, probably, with 100 feet of water over your head.

Nitrogen narcosis has also been compared to alcoholic intoxication, the so-called "Martini Law" — each 50 feet of descent is equivalent to drinking one martini. Your thinking slows down. Your inhibitions and self-control are reduced, allowing euphoria or anxiety to emerge. Perceptual narrowing and a tendency to become fixed on one idea are common. Nitrogen narcosis, like alcohol, also impairs your motor control and memory. If it progresses far enough, you become unconscious. Precisely which mental functions are impaired, in what order and to what degree are debated by researchers, and studies have yielded conflicting results. What everyone agrees on, however, is that nitrogen narcosis degrades your ability to react quickly to a crisis and reason your way out of it.

Not You? You Wish

You've been below 100 feet many times and you've never been narced? Maybe. Divers, like drinkers, vary widely in their susceptibility, and you may in fact be more resistant to narcosis than some others. But it's hard to know that for sure based on your subjective feelings. "One of the biggest effects of nitrogen narcosis is an amnesia of what happened when you were down there," says Bennett. "Divers don't even remember what they were like." So you may have been more narced than you remember. Add forgetfulness to overconfidence and recklessness, other important effects of nitrogen narcosis, and you're like the guy leaving the party after a few too many who insists he's OK to drive. He has done it before and may do it again, but only if he's not called upon to react to a sudden emergency like a sharp curve and a stout tree.

Nitrogen narcosis is related to the partial pressure of the nitrogen in your gas mix, so narcosis becomes more likely as you go deeper. You may as well say nitrogen narcosis is caused by going deep. The threshold for significant narcosis on air is often said to be 100 feet, but that's only a rough guide. Actually, narcosis probably begins to appear as soon as you leave the surface. For example, a Navy test found slight but measurable effects at only 33 feet. It's a lot like asking what blood alcohol level constitutes drunk driving. The law states a number, though everyone knows there is some effect on your reaction time at lower levels.

Nitrogen and alcohol are different in some ways too. Serious, noticeable narcosis comes on more quickly whenever you reach your personal threshold depth. Studies show it reaches a peak within two minutes, and does not get worse even after three hours at that depth. It goes away very quickly as you ascend, and totally disappears before you reach the surface. As far as anyone knows, nitrogen narcosis, unlike alcohol abuse, does not do long-term harm and leaves no hangover. However, it's not what narcosis itself does to you that you should worry about, it's the harm you can do yourself because you're too narced to think clearly.

Many Unknowns

Different divers feel different amounts of narcosis at the same depth. The same diver may feel different amounts of narcosis at the same depth on different days. Narcosis takes different forms, too. Just as there are happy drunks, sad drunks and angry drunks, some divers are euphoric when narced, but some are terrified and some are just confused.

Some of the variables affecting all divers are:

• Interaction with drugs. It is well-known that several drugs can interact in surprisingly intense ways, so that 1 + 1 equals 3. Some drugs, including anti-motion sickness pills, may interact with nitrogen to increase your narcosis susceptibility and intensity. Not much research has been done, but Bennett suggests that if a drug would increase the effect of alcohol, it's a reasonable assumption that it might increase nitrogen narcosis.

 

• Interaction with alcohol. Drinking and diving is never a good idea, of course, and some experts think the nitrogen/alcohol interaction may be especially strong because they have similar effects on your nervous system--1 + 1 may equal 5, in other words. Even a hangover can potentiate nitrogen narcosis.

 

 

• Interaction with carbon dioxide. Among the intensifiers of nitrogen narcosis, "carbon dioxide is a big one," says Bennett. "High levels of carbon dioxide in your blood are going to work with nitrogen to make narcosis worse." Elevated carbon dioxide levels generally result from rapid, heavy breathing. You may be working hard--finning into a current, for example--or sucking on a poorly performing regulator. Anxiety is another cause of rapid breathing and therefore high carbon dioxide.

 

 

• Fatigue. Doing heavy work at depth seems to bring on nitrogen narcosis, though whether that's because of the elevated carbon dioxide that usually goes with hard work or is an independent effect of being tired is not clear.

 

 

• Task-loading, time stress. Trying to do too many things, or trying to do too much in a short time, also increases the narcosis effect. Again, whether this is a carbon dioxide effect caused by the anxiety of trying to cope with too many tasks or an independent effect is not clear.

 

 

• Cold. Being cold is often mentioned as a contributing cause of nitrogen narcosis. The reasons aren't known, but some of the effects of hypothermia are similar to those of narcosis, including mental dulling, sluggishness and amnesia.

 

In addition to the variables that affect all divers, some divers seem to be more susceptible to nitrogen narcosis than others. Obviously the relaxed, healthy diver with good breathing habits and a low air consumption rate has an advantage over the nervous, heavy breather. Also, some experts think highly intelligent and emotionally stable divers are less susceptible to nitrogen narcosis.

Adaptation to Narcosis

Most divers who regularly go very deep on air are convinced that they become adapted to it and after a while have less trouble with nitrogen narcosis. Is it true physical adaptation (meaning the divers are actually less narced) or have the divers just learned to compensate better for it? That's another unknown. The adaptation, if that's what it is, is temporary. Most say it wears off in about five days.

In any event, common practice among divers who must go very deep using air is to work up to the depth by making the first dive of each day progressively deeper. In 1989, Bret Gilliam set a depth record on air of 452 feet, and worked down to the depth with more than 600 dives, at least 100 of them deeper than 300 feet. As a result, Gilliam was not so narced at 452 feet that he could not do a series of math problems and, more to the point, return to the surface alive.

How Deep Is Too Deep?

Gilliam's 452 feet on air is off the chart for the rest of us. Various studies have described the narcotic effect of air at 300 feet as "stupefaction," "severe narcosis," "marked impairment of practical ability and judgment," and even unconsciousness. Other reports: "severe impairment of intellectual performance" at 230 feet; "sleepiness, illusions, impaired judgment" at 165 feet; and "idea fixation, perceptual narrowing and overconfidence" in the 100- to 132-foot range. Probably the customary 130-foot limit for recreational diving in the U.S. is a good one until you know better your personal susceptibility to nitrogen narcosis and have trained yourself in coping with it. For diving much deeper than that, trimix (in which most of the nitrogen is replaced with less-narcotic helium) is probably a safer gas.

How To Tell If You Are Narced

That's tough because your judgment, the faculty you depend on to tell you if you are affected, is the first to be attacked by the narcosis. Returning to the analogy to alcohol, it's like asking how you can tell if your driving is affected after you've had a few drinks. In both cases, you should probably just assume it.

Some divers experienced with deep water like Gilliam have developed their own versions of roadside sobriety tests. Not foolproof, but better than nothing:

• Every few minutes, check your depth and tank pressure, and write them on your slate. Check your buddy's depth and pressure and write them on your slate. Your buddy does the same on his slate. Now each of you has to point to your own and your buddy's numbers on both slates, and the slates have to agree. This test automatically compares both divers, which can be valuable if one diver is narced and the other is not.

 

• Every few minutes, hold up a number of fingers to your buddy (say, three fingers). He has to respond with the same number plus one (four fingers).

 

These "roadside" tests aren't foolproof because many of the effects of mild to moderate nitrogen narcosis can be overcome, or at least masked, if you try hard enough. Your mind can be impaired, but if you devote all your diminished resources to one job, you can do it well. This can drive researchers crazy. In one case, subjects in a chamber at a "depth" where they should have been narced performed the tests better than at the surface. In other studies, narced divers have often been able to attain good accuracy at the expense of speed, or vice versa. This means you might be able to perform the match-slates test or the count-fingers test and still be narced. So watch your responses (and your buddy's) for both accuracy and speed.

You are like the drunk driver who, by fierce concentration, is able to keep his car between the white lines. Obviously, the greater danger for both of you is the unexpected, not the routine. It's the entanglement or a regulator free-flow, the sharp curve and the tree. So leave the nitrogen party early and dive carefully. Mom's right: There is such a thing as too much fun.

How To Beat Narcosis

Start by assuming you will be narced if you go deeper than 100 feet. You can't prevent nitrogen narcosis entirely, but you can minimize it and compensate for it.

• Be clean and sober. Avoid over-the-counter meds like Sudafed and Dramamine if you can, because they may potentiate the narcotic effect. It goes without saying that you shouldn't drink and dive, but even a hangover from last night's drinking can make narcosis worse and reduce your ability to cope with it.

 

• Be rested and confident. Fatigue and anxiety may help trigger narcosis, and certainly are stresses that diminish your ability to solve problems.

 

 

• Use a high-quality regulator in good condition. High breathing resistance elevates your carbon dioxide level, which potentiates narcosis.

 

 

• Avoid task-loading. Don't try to do too much, because that causes stress and anxiety. Your first excursion below 100 feet is not the time to figure out a new camera housing, for example, because it will divert your diminished mental capacity from what's most important—diving safely. Keep it simple, stupid, because stupid you will be.

 

 

• Be overtrained. Most of us never practice the basic safety skills like air sharing and weight dumping because they seem so simple. But under the influence of narcosis, the simplest tasks become more difficult. If you have to think about it, you may not be able to do it, and your repertoire of skills may be stripped down to those made automatic by frequent rehearsal.

 

 

• Approach limits gradually. Don't go to 130 feet until you've been to 110 a few times, seen how you react and become comfortable with the depth. And descend slowly, as there is some evidence that rapid compression makes narcosis more severe.

 

 

• Use a slate. Don't depend on remembering the dive plan or the camera controls; write them down. That frees up mental RAM for coping with the dive itself. And a slate is useful for narcosis tests like writing down depth and tank pressure.

 

 

• Schedule gauge checks and buddy checks. Don't check your tank pressure only when you think of it. Plan to check at stated intervals, say every two minutes. Likewise, plan to look for your buddy and make eye contact on a schedule, like every minute. Discipline helps keep you focused, and if either of you consistently misses appointments, suspect narcosis.

 

 

• Be positive and motivated. Experiments have shown that divers who want to conquer narcosis and believe they can, actually do. At recreational depths, narcosis is fairly mild and controllable. The key is to be optimistic but prepared, confident but prudent.

I have spent much of the last 30 years underwater. I’ve explored the deep on thousands of scuba dives and numerous submersible trips to 18,000 feet [5,500 meters] below the surface. Yet during all these journeys, I have only rarely encountered some of the ocean’s biggest mysteries: deep-sea sharks.

Twenty-seven years ago, a small cable outfit broadcast a week of television all about sharks. In the many years since, while the Discovery Channel’s Shark Week has not shied away from controversial shows depicting attacks, it has also brought sharks into the public consciousness and educated the public about their importance to our oceans.

The casual fan of Shark Week can probably name the big three: the great white, tiger and bull sharks. They are the DiCaprio, Clooney and Pitt of the shark world. As important as these are, they are just three members of the shark family, which includes over 400 species. To me, the most amazing sharks are the little-known species that lurk in the deep sea.

Over the years, we’ve learned quite a bit about shallow-water sharks because they’re in the reef — in the dive zone where we can see them. Deep-sea sharks seem almost alien to us because they’re so deep in the ocean that it’s hard to get there and observe them. The pressure is extremely high, temperatures are extremely low and only in the last several decades have we had underwater vehicles, robots and submarines that can get down into these depths.

Here are some of the few things that we do know about them:

Goblin shark: One of the strangest-looking fish in the ocean, very few specimens have been caught and studied. It was first found in Japan, but is probably widely distributed in the deep sea. Frill shark: This true example of a living fossil is typically never found in shallow water; when it is, it’s usually in distress. Eel-like in shape, and up to 6 feet [1.8 meters] long, they can distend their mouths open and eat things that are more than half their body length.

Bluntnose sixgill shark: This shark can grow up to 16 feet [5 meters] long and 1,300 pounds and can attack like a great white shark, but with a stronger bite. Though primarily a deep-sea species, some make trips to the shallows at night, allowing for the unsuspecting night-diver to chance upon them.

Greenland shark: This is one of the largest sharks in the world, reaching up to 24 feet [7.3 meters] in length. It is probably the most northern-ranging of shark species, living mainly in deep, very cold water of the high North Atlantic and Arctic Oceans The species has been found at a depth of more than 7,000 feet [2,130 meters], yet stomachs of some specimens have contained polar bear, pieces of horse and even an entire reindeer. Whether those animals were eaten at the surface or scavenged from the bottom is not known.

Megamouth shark: This species was only first discovered in the ocean in 1976; with only about 50 sightings worldwide, it remains one of the poorly known sharks. This species filters plankton from the water, a feeding mode that it may have evolved independently from the two other known filter-feeding sharks, the basking shark and whale shark.

We know that all sharks are important to human well-being. Some evidence of this is well-proven; other potential benefits remain unstudied. We know that sharks keep the food web in check and are a vital part of healthy fisheries. They boost local economies through ecotourism, have the potential to cure a variety of diseases, are a vital part of the carbon cycle and inspire smart design in items ranging from swimsuits to mechanisms that harness wave energy.

Studying deep-sea sharks in particular could bring us valuable knowledge. Science is on the cusp of understanding the power of genomes in nature. These deep-sea sharks, along with other specialized deep-sea organisms, including bacteria and worms that live on the seafloor, contain an infinite encyclopedia of genetic knowledge that has allowed them to survive in the most extreme environment on our planet. Their evolutionary secrets could open doors to understanding our own existence and survival on Earth.

One thing we do know is that sharks in all parts of the ocean are under pressure from human activity. Overfishing and unsustainable practices, like shark finning, account for the death of an estimated 100 million sharks per year. Even these deep-water dwellers face these threats.

The oceans’ depths are no doubt hiding many more secrets that human beings have yet to lay eyes upon. The Megalodon — an extinct shark the size of a school bus — may be gone, but there is still a whole range of deep-sea sharks in our oceans waiting to be studied, with probably others waiting to be discovered. As long as we can give them the same attention and protection we give to great white, tiger and bull sharks, I know there is much we can learn from them about how our oceans work.

Noise pollution has now become one of the common themes of human-generated impacts on the ocean. Shipping noise, military sonar, and seismic airgun surveys are increasingly becoming part of the public discussion in marine conservation. These noises are easy for us to understand; they are loud, ubiquitous, and they are all in the range of human hearing. We can all imagine what it must be like having an expressway of supertankers and cargo vessels plying the shipping lanes over our heads, or being subjected to ear-piercing tactical sonar signals.

But there is a flood of noises creeping into the ocean that, while we humans can’t hear them, may prove equally as insidious as the loud noises that we can hear. Dolphins, porpoises, beaked whales, and sperm whales – the “toothed whales”–use high frequency bio-sonar, so their sound frequency sensitivities reach well above the frequencies that we humans can hear.

Some of their fish prey can also hear these higher frequencies as an adaptive measure against predation. And while we don’t yet have evidence of seals using bio-sonar, we do know that many seals also hear sounds well above the highest frequencies that humans can hear.

While marine technologists don’t seem to be giving it a lot of thought, our sonar technologies are increasingly crowding out these higher frequency bands with underwater acoustical beacons, echo sounders, and underwater communication systems. The spectrogram below (and the ones accompanying the sound examples) is a method of visualizing sound with time on the horizontal “x” axis, and frequency on the vertical “y” axis. The lower frequencies are closer to the bottom.

This particular spectrogram from NEPTUNE Canada displays a year of sound near the sea floor in the ocean off of Vancouver Island.

In the figure there is a thick cyan line just between the 30 kHz and 40 kHz index lines going across the entire year. This is from an upward-looking echo-sounder used to measure ocean currents. This signal is way above our hearing range, so we call it “ultrasound.” But this sound is right in the middle of the hearing range of orcas, dolphins, and porpoises.

The echo-sounder signal is not complex, but it is persistent. Communication signals on the other hand are necessarily complex and can sound quite obnoxious (these examples are in the human auditory range).

Increasingly, these types of sounds are being used to control equipment, report on sensor conditions, and even monitor the movement of tagged sharks. Given that some of these high frequency signals are designed to broadcast up to 10 kilometers (6 miles), the increasing density of these signals in the ocean may be cropping up as a problem for the animals that can hear them.

Yet relief may be within reach. While the ocean is getting louder with the sounds of mechanization and technology, it was not necessarily quieter before the industrialization of shipping. The ocean was probably a pretty noisy place before the 20th century due to biological noise. Since the industrialization of whaling and fishing millions of whales and perhaps 90% of all fish have been pulled out of the sea–along with all of their noises.

The difference, of course, is that these “legacy noises” were natural. This may or may not be significant with the broad-band mechanical noises of ships or the loud pulsing of seismic surveys, but it is possible that technical communication signals could be crafted to sound more like animal communication sounds, and less like the antagonistic sounds currently in use.

We know that some of these community animals can be quite loud, and that for the last 30 million years they have been swimming around in large groups. If technical communication signals sounded more like animal communication signals they may fit right in!

Subsea telemetry acoustic transceivers used in offshore oil operations (Illustration: Nautronix)

–

Michael Stocker on Alaska Bowpicker

Michael is the founding director of Ocean Conservation Research, a scientific research and policy development organization focused on understanding the impacts of, and finding technical and policy solutions to the growing problem of human-generated ocean noise pollution. He is a technical generalist conversant in physics, acoustics, biology, electronics, and cultural history, with a gift for conveying complex scientific and technical issues in clear, understandable terms.

He has written and spoken about marine bio-acoustics since 1992, presenting in national and regional hearings, national and international television, radio and news publications, and in museums, schools and universities.

His book titled “Hear Where We Are: Sound, Ecology, and Sense of Place” is published by Springer. The book reveals how humans and other animals use sound and sound perception to establish their placement in their environment, and communicate that placement to others.

The ballast weight you carry doesn't change during a dive, but it's often the biggest problem for divers who struggle with perfecting neutral buoyancy. Many divers are overweighted for the type of diving they do, carrying more lead than they need. That makes buoyancy control more difficult because every extra pound of lead has to be balanced with an extra pound of buoyancy. 

But because the air in your BC expands and contracts with depth changes, you have to be constantly adding or subtracting air from your BC. So extra lead means extra thrust up or down when you change depth, and requires extra fiddling with your BC valve controls. Sometimes it means nearly constant fiddling.

Here are our tips for taking off that extra weight.

Just do it. Take off two pounds before your next dive. Can't get below the surface? Before you reach for the lead again, make sure you really need it. Getting below the surface, especially on the first dive of the day, can be surprisingly difficult and can trick you into carrying more lead than you really need. 

Be patient. The plush lining of a dry wetsuit can trap a surprising amount of air, and therefore buoyancy, in its fibers, and it takes a minute or so to get fully wet.

Reach up. Hold the inflator hose over your head and stretch it upward a little so its attachment point to your BC is highest. At the same time, says Linda Van Velson, a PADI course director, "dip your right shoulder and squeeze the BC against your chest with your right arm." This maneuver encourages the last few bubbles to find the exit.

Rock backward a little. Many BCs trap a bubble of air just behind your head. Rocking backward as if you are in a La-Z-Boy recliner moves the exhaust hose over the bubble and lets it escape.

Relax. Many of us move our hands and feet more than we realize, especially at the beginning of the dive. To counteract that, hold your right arm still at your side (your left is holding up your exhaust hose), extend your legs and point your fins straight down so they have the least resistance to sinking.

Exhale. Another tendency is to hold your breath, and a lungful of air adds as much as 10 pounds of buoyancy. Exhale and hold it until you start sinking, then take shallow inhales until you get below five feet.

Force it. Another option is to use your body weight to generate some downward momentum by lifting part of it out of the water, then letting it fall back. Lying on your face, jackknife your upper body downward, then lift one leg, then another, out of the water. The weight of your legs will drive you downward, and once your fins are in the water you can kick down.

Use the line. If the dive boat is tied off at a mooring, use the line to help pull yourself down. This trick also works for divers who need to go down slowly to equalize. 

Get a little help from your friends. Ask your buddy to gently tug your fin and pull you down for the first few feet of your descent. Usually, by the time you're in 10 to 15 feet of water, you should sink without help.

What's the ideal amount of weight? Use our Buoyancy Calculator to determine what's right for you.

Read our Tips on Neutral Buoyancy for more secrets on achieving a the feeling of weightlessness underwater.

A leaky mask has got to be the most annoying thing a diver has to  deal with when trying to enjoy a dive (with a fogged-up mask coming in a close second). So any extra effort you can invest in the dive store fitting a new mask to your face is definitely time well spent. 

However, the standard dry-fit procedure of centering the mask on your face, making sure all skirt edges are in contact with your skin, then inhaling gently —without the strap attached — to see whether you can get an airtight seal, won’t necessarily guarantee that you’re going to have a leak-proof dive. While some lucky divers are able to put their masks on and hit the water and never touch their mask for the entire dive, for most of us, getting our mask fully sealed takes a little finesse. We've got some tips to avoid those annoying leaks:

• After giant-striding into the water and popping to the surface, take a moment to remove your mask, give your head a good double-dunking, and hand-squeegee your hair back and away from your face. Then, position the mask on your face before stretching the strap over your head. If you’re wearing a hood, you can forgo the hair step as long as no renegade strands are sticking out. But run a finger around the edge of the hood opening to make sure the mask skirt is against your skin and not overlapping the neoprene.

• Double-check to make sure the mask is properly centered on your face. If it’s not, you probably will break the seal once you start diving. Also, double-check the position of the strap on the back of your head. If it it's too high, it tends to lift the bottom of the skirt; if too low, it affects the top of the skirt. If it's too tight, it can distort the shape of the skirt — that can break the seal too. 

• Just before descending, push the mask lens inward, forcing some air out and creating a good air pressure seal. Now you’re ready for your descent. Once under water, if the seal is sound, water pressure should take over and you should be good to go. At some point, you’ll probably want to nose-blow a little air back in to avoid getting mask squeeze as you go deeper.

By following these steps, hopefully you’ll be able to pull off a dive without having to contend with water constantly seeping — or gushing — into the mask. If not, you might want to consider investing in a purge mask.