In reply to KeithW:
Similar story, and I only have a rough memory of it, but the crux was: diver and buddy on a scooter head into a cave but the scooter dies on them, followed by the second scooter. At this point they sensibly decide to abandon the dive and start swimming back. From what can be made out, due to the increased exertion of now having to swim one air bottle was used and they proceeded to buddy breath....not much further up masks, flippers and torn bits of wetsuit were found and one of the bodies had scratches to the face. Not much further up the second body was found. Apparently they had fought for the last remaining air, but were still 8 minutes from their left full tank.
On another note, there was cave diving story I read once where rain flooded the cave and the 3 divers stirred up silt and couldn't find their way out. Ended up in a dead end that gradually flooded. Light ran out, breathing became difficult and they knew they would die. The description of their panic and mental state at the time was pretty horrifying. Fortunately they were rescued pretty much in the nick of time, but as far as they were concerned, they were simply waiting to drown.