TDI certified me to dive to 55m / 180ft on air (
https://www.tdisdi.com/tdi/get-certified/extended-range-diver) and DAN insure me within that certification so I'll be pretty disappointed to learn that both are comfortable with me diving to within five metres of as significant a risk of death as this thread suggests cos I've done 62m and spent plenty of time in the 50's.
On the way back from a PNG dive trip yesterday I was reading a book called "The last new Guinea Salvage Pirate" by Fritz Hersheid, set in the 60's and 70's - the things they did back in the day... this is extraordinary ;
"As we got deeper George (Tyer) started to get serious and turned to face me, keeping very close, looking into my eyes, watching for any signs of narcosis. We leveled off at the 250 ft mark and George gave the OK signal. I responded positive. After a short dive along the wall we slowly returned to the surface. And that was that. After just five dives I was a certified diver".
An earlier dive required him to do an emergency free ascent from "at least 150 ft". George was pretty hard core. Yeah nah...
Fritz then convinced his girlfriend Janice to learn to dive with George and she took to it well so that George said he'd waive the fee if she agreed to try for the female world depth record on air. And buoyed by the five dives under her belt she agreed. Apparently they were all well aware of oxygen toxicity and did all their diving off navy tables and if they wanted to 'cheat', they used the less conservative French ones.
Anyhoo, after a few 250 ft dives to 'acclimatise' Janice to narcosis, plus a few at 280 ft for luck, they were ready to try for the record at 320 ft when another woman - Kathy Trout, awesome name for a diver - upped the record to 328 ft. Unphased, George simply bumped his student's goal to 340 ft (103m) at which point Janice finally said 'enough'. Apparently she thought it a teeny bit deep for a new OW student.
As much as George sounds like he wanted her dead, he himself air dived to 350 ft so he walked the walk. That's a PPO2 of over 2.3(!!!) - we're only talking 1.47 in this thread and jaws are dropping. Obviously you should be experienced and plan and prepare deep air dives, but that's exactly why we take courses like TDI Extended Range, and the deco procedures prerequisite before it, and the advanced nitrox prerequisite before that and the advanced wreck and so and so on, all of which put you through a ton of planning and executing dives (in gauge mode), assessing your behaviour at depth, testing how affected you are by narcosis with puzzles etc, asking you to perform tasks, and at least one of which requires you to have at least 30 dives deeper than 30m in your logbook first.
The part of this thread that gives ME the shivers is "single tank" and poor gear. I'm pretty sure people who get certified to do deep air dives will have appropriate gear in top condition.
