The diving boat captain had told Tony Maffatone there would be extra tanks of gas suspended from the boat at 70 feet. But when he reached the chilled, murky waters above shipwrecked Andrea Doria 100 miles off the coast of Long Island, N.Y., there were no tanks to be found. He scouted a while, but then, checking his air gauges, began swimming to the surface.
By the time he reached 20 feet, Maffatone was out of air. He grasped one of the emergency lines of gas dangling just below the boat, shoved a mouthpiece in his mouth and sucked in some pure oxygen.
"I was hanging there thinking, 'this is not good,' remembers Maffatone. It was a close call he never wants to face again.
Maffatone was one of the lucky ones.
In recent years shipwreck diving has led to an unsettling string of deaths. In the last two summer seasons five divers probing the decaying remains of a single shipwreck -- the Andrea Doria -- lost their lives. And since January 2000, the Divers Alert Network has recorded at least 27 diving deaths in the U.S. The network's director, Peter Bennet, is not sure how many of those deaths occurred during shipwreck dives. But he admits that shipwreck diving, like underwater cave diving, carries its risks.
"If you're in a wreck and you don't know your way out, then you don't ever come out," he says.
Where Air Becomes Lethal
What makes shipwreck diving appealing is also what makes it so dangerous. Wrecks, for example, can sink to extreme depths. The Andrea Doria is known as the "Mt. Everest of diving" partly because it's an intimidating 180 feet below the water's surface. And that's only to the top of the wreck.
At such depths, breathing gets very complicated.
Unlike on Everest, where oxygen levels are thin, the weight of water at more than 20 feet deep compresses the oxygen that divers breathe. That oxygen density, in turn, wreaks havoc on the human nervous system and can lead to unconsciousness and eventually death.
Nitrogen also takes on deadly traits underwater. Again, the weight of water -- about 64 pounds per cubic foot -- is what transforms this otherwise harmless gas. As a diver plunges deeper underwater, excess nitrogen is compressed in the bloodstream. If divers rise too fast to the surface, the compressed nitrogen expands and can fizz out of the bloodstream, entering the spinal column and causing an extremely painful and sometimes deadly condition known as the bends.
Nitrogen's other underwater effect is a little more pleasant, but equally lethal.
"We call it the whiskey factor," says Bielenda. "At every 50 feet of depth it's like taking a shot of whiskey."
While an alcoholic buzz may be an appealing sensation on land, losing your senses underwater can lead to fatal accidents. And shipwrecks hold plenty of potential for accidents. As Bielenda points out, underwater wrecks are nothing more than a tangle of lines and rotting structures that present a deadly maze to divers.
"Imagine a ship on its side, fill it up with mud and dirt and water, tear it apart so all wire is hanging loosely and what do you have? It's a horror show," he says.
Diving Distracted
One device divers use to avoid getting snared or disoriented in a wreck is a guideline, or coiled string, that they tie along their path. Like a trail of bread crumbs, the guidelines allow them to retrace their route.
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