There are a handful of old-school Corsican divers who dive on air at depths well below 170 feet. They're professional Mediterranean red coral harvesters. Many have died, goes without saying. I recently saw a program on French TV of this guy in his 50s still doing it with his 7mm wetsuit and his double + a pony, going down to 100 meters. On air. He stays about 3 minutes picking the red coral off the ceiling of caves and rocks, fills his basket, shoots it up with his balloon and up he goes for 2 hrs and change. He's got his mate up on the boat watching his bubbles and as the time draws near the 12 meter deco stop, he throws him a hose running hot water that the diver slips in his wetsuit through the hood and a hookah. There are a bunch of stage bottles strung out from the 12 to the 3 meter deco stops along the ascent line, but I don't remember seeing much Nitrox or O2. Theses guys are legends, but like I said they don't live to be very old. The availability of Nitrox and more importantly Trimix will probably help the younger generation stay alive a little longer. If only the red coral could enjoy the same benefits...
Edit: I just watched the show again (I'd taped it) and the old Corsican dude was on Trimix, so my mistake (and that's probably why he's still diving - or alive). And he stayed 15 minutes at 104m, had one safety stop at 50m, then 25/12/9/6 and 3m.
