The first dive to a depth of a thousand feet was made in 1962 by Hannes Keller, an ebullient twenty-eight-year-old Swiss mathematician who wore half-rimmed glasses and drank a bottle of Coca-Cola each morning for breakfast. With that dive Keller broke a record he had set himself one year earlier, when he briefly descended to 728 feet. How he performed these dives without killing himself was a closely guarded secret. At the time, it was widely believed that no human being could safely dive to depths beyond three hundred feet. That was because, beginning at a depth of one hundred feet, a diver breathing fresh air starts to lose his mind.

This condition, nitrogen narcosis, is also known as the Martini Effect, because the diver feels as if he has drunk a martini on an empty stomach—the calculation is one martini for every additional fifty feet of depth. But an even greater danger to the diver is the bends, a manifestation of decompression sickness that occurs when nitrogen gas saturates the blood and tissues. The problem is not in the descent, but the ascent. As the diver returns to the surface, the nitrogen bubbles increase in size, lodging in the joints, arteries, organs, and sometimes the brain or spine, where they can cause pain and potentially death. The deeper a diver descends, the more slowly he must ascend in order to avoid the bends.

In 1956 a Royal Navy boatswain had successfully dived to six hundred feet, breathing a mixture of helium and oxygen to avoid nitrogen narcosis, but he took twelve hours to resurface. Keller, by comparison, returned to the surface after his first record dive in less than an hour. He boasted of using “secret” mixtures of gases for his underwater breathing apparatus, with different mixtures designed for different depths, but wouldn’t disclose exact figures. After an editor from Life, who had accompanied Keller on his 728-foot dive, wrote an article about their accomplishment, the US Navy took interest. So did the Shell Oil Company.

The Navy gave Keller $22,000 to finance the thousand-foot dive. Shell provided an experimental offshore drilling ship called the Eureka and a decompression chamber; at the time Shell had already begun to drill offshore, but only to a depth of 250 feet. Keller chose as his diving partner another journalist, Peter Small, the thirty-five-year-old editor of Triton magazine (now Diver) and a founder of the British Sub-Acqua Club. The dive took place in Southern California, off Santa Catalina Island; Keller and Small planned to be the first men to set foot on the Continental Shelf. Observers aboard the Eureka included several officers from the US Navy’s experimental diving program; a group from Shell Oil; two young safety divers; and Mary Small, Peter’s twenty-three-year-old…