Worked the sett tanks at gosport but I think it's all gone now and submariners from all over the world used it. They had to breath out on the way up otherwise they'd do themself a proper mischief and that's were us bubble-heads came in. Boyles Law of partial pressure. Must have been a terrible end that the poor young lads faced and not a hope in hell at those depths.Some fascinating stuff regarding rescues from stricken subs.
Personally you wouldn't get me in one for all the weed in Morocco but the life of a submariner is a tough one. Got a mate who did the whole cold war, sneaking around, under for months stuff with RN.