"The Last Dive".The book "Shadow Divers" documents a very tragic incident involving a father and son (expert cave divers) who died due to an incident inside the submarine wreck. The factors that killed them could never have killed them in their primary environment "Cave." They placed their deco bottles outside the submarine. Son went inside and did not realize that furniture can fall on you! He tried to get a map from under a cabinet and tried to move it and it fell on him trapping him underneath. When he did not emerge in the appointed time, father went in after him. It took a long time to move the cabinet to pull him out. When they came out of the submarine, the could not find the deco bottles! Cavers place them at the entrance and it is waiting for them on the way back. Cant miss it. Placing it in a submarine wreck on its side turned out not to be so convenient. They missed the bottles, missed the stop and came to the surface and died. Their blood had turned into sludge.
I used to think that overheads are overheads but that story made me realize that cave is cave and wreck is wreck.
They were using AIR on a 70m deep wreck.