(April 1, 1949 – April 6, 1994)
An American Cave Diver widely recognized for his dedication and his explorations in the world of the underwater caves. Exley began diving in 1965 at the age of 16. That same year he entered his first cave and was hooked on diving in caves for the rest of his life. To finance this passion, Exley worked as a math teacher in the Suwannee high school in Live Oak, Florida. In the spring of 1973, Exley served as an aquanaut during eight-day aboard the Hydrolab underwater habitat mission in the Bahamas.
On February 6th, 1974, he became director of the section of cave diving at the Cave Diving Section of the National Speleological Society. During his career, he established safety procedures which persist in scuba diving until today. Exley was also a pioneer in deep scuba diving. For purposes of rescue during cave diving, Exley helped to standardize the usage of the “Octopus.” Which is a redundant second stage diving regulator that can be used as a backup in the event the diver’s primary second stage fails, or, to allow the diver and his buddy to have simultaneous access to the diver’s gas if the buddy has an out-of-gas emergency. The Octopus is considered an essential tool for all recreational and technical divers. Exley was the first to log over 1000 cave dives (at the age of 23); at 29 years old, he already had over 4000 dives. Sheck Exley had an exceptional resistance to nitrogen narcosis and was one of the few divers to survive 400-foot (120 m) open water dive on pure compressed air. Playing a role as a safety diver for two divers trying to set an air-only depth record in 1970, Exley reached 465 feet (142 m) in salt water, but couldn’t go deeper due to nitrogen narcosis and the start of a blackout. The two record-depth attempting unconscious divers died just out of reach beneath him, and such air-depth records are no longer sought or recorded. During his diving career, he set many depths and cave penetration records. Exley is among eleven people of technical scuba diving to reach depths of more than 800 feet (240 m), as well as the first. His carefully planned multistage decompressions from these dives, in open water (not in decompression tank) sometimes required more than 13.5 hours. However, he never suffered from a classic decompression sickness in his diving career. Exley and the German diver, Jochen Hasenmayer, became friends and rivals in the 1980s, each repeatedly attempting to break the depth records of the other. Exley died on April 6, 1994, at the age of 45, while trying to descend to a depth of over 1,000 feet (300 m) in a freshwater cenote in Tamaulipas, Mexico, or sinkhole, called Zacatón. He made the dive as part of a dual dive with Jim Bowden, but Bowden aborted his descent early when his gas supply ran low. Exley’s body was recovered when his team of divers pulled the rope where he had his unused decompression tanks. It was found that he had looped into the descent line, perhaps to sort out gas issues or other gas problems. His wrist-mounted dive computer read a maximum depth of 906 feet (276 m). The cause of Exley’s death could not be determined. His team concluded that the causes “… could include the stress of HPNS exacerbated by the narcotic effects of nitrogen at that depth”. The line was also wrapped (deliberately) around Exley’s tank valves. Bowden and other experts have theorized that Exley may have done this in anticipation of his death to prevent any dangerous body recovery operations. In the books, Diving into Darkness (about Dave Shaw and Don Shirley), the comments of the author: “Exley status is nearly impossible to overcome.”