Shadow Divers: The True Adventure of Two Americans Who Risked Everything to Solve One of the Last Mysteries of World War II

by Robert Kurson

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 to the twilight of a waking anesthetic, still others to the fog of ether or laughing gas. Symptoms are relatively mild at shallower depths—judgment skews, motor skills dull, manual dexterity suffers, peripheral vision narrows, emotions heighten. As a diver descends farther, the effects intensify. At 130 feet, or about five atmospheres, most divers will be impaired. Some become all thumbs and struggle to complete simple tasks, such as tying a knot; others turn “dumb with the depth” and must talk themselves into believing what they already know. As a diver descends even deeper, say to 170 or 180 feet, he might start to hallucinate, until lobsters begin beckoning him by name or offering him unsound advice. Sometimes divers realize that they are “narced” by the sounds they hear. Many experience the “jungle drums,” the deafening sound of one’s pulse in one’s own ears; or they might simply hear a hum, like a buzzing alarm clock lost under a pillow. Below 200 feet, narcosis can supercharge the normal processing of fear, joy, sorrow, excitement, and disappointment. Tiny problems—a missing knife, a bit of silt—can be perceived as unfolding catastrophes and snowball into panic. Serious problems—a depleting air tank or the loss of the anchor line—can appear as n...