ever been in nice north atlantic storm on a sub? I have. The old boat sailors had brass balls. They had to ride their boats on the surace in storms, taking water down the hatch, running stinky diesel motors. Then, when they dove, which was normally only for a few hours, they were still rocked around terribly. You don't get much relief from surface swell until you get down fairly far, say deeper than 200 feet during a good storm. Of course, you never really dry off, and oily slime spread throughout the boat. Sheesh, the most impressive thing is that they could hit targets with essentially visual solutions. Those guys sure knew their craft, right or wrong.
Even on a modern sub you can't get away from the smell - it permeates everything. When you get away from the boat for a while and open some of you things that were on the boat -- whew! there it is!
the germans had it the worst from a loss perspective, I think 36000 of the 39000 who sailed never returned. Something like that. Astounding.