The Atlantis Series and Other Deep Dives.

Abstract

Introduction: Diving deeper into the water became operationally important at the turn of the century, with the availability of more sophisticated breathing equipment and the use of compressed air from the surface. Practical limits were investigated by Haldane (Boycott et al., 1908) and set at a useful depth of 90 fsw in well-trained individuals, because of the onset of severe narcosis, leading to reductions in manual dexterity and severe mental impairment. It was noted, however, that brief exposures were better tolerated. A proposal in the U.S. Navy by Thompson (1919) to utilize helium as inert gas at greater depths because of reduced breathing resistance did not achieve success because of the reluctance of operators to abandon "safe" air tables and the unexpected risks of the decompression. It was left to two individuals working alone outside the U.S. Navy, Mr. Nohl and Dr. End, to demonstrate the practical use of helium-oxygen mixtures into a solo dive to 420 feet in Lake Michigan (Nohl, 1938). The U.S. Navy acknowledged the practicality of heliox diving by rapidly adopting this gas in a large multiperson rescue operation in 1939 to 243 fsw for the salvage of the crew of the submarine USS Squalus in the open sea.