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To those few, it is not a matter of if they will taste death, only of whether they’ll swallow. If a deep-wreck diver stays in the sport long enough, he will likely either come close to dying, watch another diver die, or die himself. There are times in this sport when it is difficult to say which of the three outcomes is worst.
    Deep-shipwreck diving is unusual in another respect. Because it confronts man’s most primordial instincts—to breathe; to see; to flee from danger—the layperson need not strap on the equipment in order to appreciate the peril. He need only contemplate the sport’s dangers. They are his dangers, too, and in learning about them he will begin to comprehend the deep-wreck diver and feel his stories. He will understand why capable men give up underwater. He will know why most people in the world would never consider chasing a fisherman’s numbers sixty miles out and 200 feet down into the middle of nowhere.
    A deep-shipwreck diver breathing air confronts two primary dangers. First, at depths greater than about 66 feet, his judgment and motor skills can become impaired, a condition known as nitrogen narcosis. As he descends farther, the effects of narcosis become more pronounced. Beyond 100 feet, where some of the best shipwrecks lie, he can be significantly handicapped, yet he must perform feats and make decisions upon which his life depends.
    Second, should something go wrong, he cannot simply swim to the surface. A diver who has spent time in deep water must ascend gradually, stopping at predetermined intervals to allow his body to readjust to decreasing pressures. He must do this even if he believes himself to be suffocating or choking or dying. Panicked divers who bolt for “sunshine and seagulls” risk a case of decompression sickness, or the “bends.” Severe bends can permanently handicap, paralyze, or kill a person. Divers who have witnessed the writhing, screaming agony of a bad bends hit swear that they would rather suffocate and drown on the bottom than surface after a long, deep dive without decompressing.
    Nearly all the myriad other dangers lying in wait for the deep-wreck diver involve narcosis or decompression sickness. Both narcosis and decompression sickness are conditions born of pressure. At sea level, atmospheric pressure is roughly equal to the pressure inside the human body. Throwing Frisbees on the beach or riding a bus, we are said to be at one atmosphere of pressure, or 14.7 pounds per square inch. Life feels normal at one atmosphere. The air we breathe at sea level, which is composed of 21 percent oxygen and 79 percent nitrogen, also enters our lungs at a pressure of one atmosphere. The oxygen nourishes our blood and tissue. The nitrogen is inert and doesn’t do much of anything.
    Things change in water. Every 33 feet below the surface, the pressure increases by one atmosphere. A scuba diver chasing seahorses at 33 feet, therefore, is said to be at two atmospheres, or twice the pressure he experienced at the surface. He barely feels it. But something is going on in the air he breathes from his tanks. While that air is still made up of oxygen and nitrogen molecules in that 21:79 ratio, there are now twice as many of each of those molecules in every lungful of air he breathes. At three atmospheres, there are three times as many oxygen and nitrogen molecules in his lungful of air, and so on.
    As the diver breathes underwater, the extra nitrogen molecules being taken into his lungs don’t just sit around as they do in a person on land. Instead, they dissolve into the bloodstream and travel into his tissues—his flesh, joints, brain, spine, everywhere. The longer and deeper a diver stays underwater, the more nitrogen accumulates in those tissues.
    At a depth of around three atmospheres, or 66 feet, that accumulated nitrogen begins to have a narcotizing effect on most divers. That is nitrogen narcosis. Some compare the effects of narcosis to alcohol intoxication, others