In the mid-to-late 1980s, small groups of experienced divers led by pioneers such as Dale Sweet, Jochen Hasenmayer, Sheck Exley, Bill Gavin, Parker Turner, Bill Main, Lamar English, Stuart Clough, Rob Palmer, Olivier Isler, Billy Deans and others began experimenting with helium mixes to push the limits of self-contained diving still further.
Below from top: Early players in the development of technical diving: Dr Bill Hamilton (right) with Kathy Hamilton and Michael Menduno in 1993; Kevin Gurr (left) presenting at the aquaCorps tek.93 conference; Carmellan Research founder Stuart Clough (left) and Rob Palmer prepare to dive Carmellan’s CR155 rebreather at Andros Island in the Bahamas.
Diving physiologist Dr RW “Bill” Hamilton and others such as anaesthesiologist John Crea, UK engineer Kevin Gurr and COMEX diving consultant Jean Pierre Imbert aided them by providing special mix decompression tables.
If you went to seek Dr Bill’s help with a mix dive, he would first try to talk you out of it and explain all the risks. If he couldn’t talk you out of it, and he was convinced that you weren’t going to kill yourself, he would agree to help.
It seems remarkable today that explorers such as Exley were conducting mixed-gas cave dives as deep as 189-274m in the mid-to-late ’80s, before most of the sport-diving community could even spell nitrox, let alone appreciate its use.
The fact that the cave environment offered confined water and ample areas for staging cylinders (and decompressing) made it a more accessible proving ground for mix technology than open water.
The wreck-diving community was also engaged in extensive exploration, and was pushing air limits with relatively short 15-25 minute dives to 61-79m. Most of these dives were conducted on air using US Navy tables or dive computers, and in the early days few if any wreck-divers were using oxygen for decompression.
Billy Deans, who owned a Key West Florida dive-shop, began developing mix protocols after losing his best friend on an air dive on the Andrea Doria wreck in 1985.
That same year, he helped Capt Steve Bielenda install an oxygen decompression system on Bielenda’s boat the rv Wahoo, based in Montauk, New York, that got divers out of the water faster and with fewer bends.
Soon everyone was decompressing with oxygen. Deans went on to create the first technical-diving training centre, and trained many north-eastern wreck divers to dive mix.