Most sub losses in WWII (and before, and since, actually) were lost with all hands. Crews train to escape but they joke about the futility of the training. Think of Kursk, lost to a hot torpedo.
If something opens the sub to the sea and the compartments are not all sealed, sayonara. The good news, I guess, is not having survivor's guilt.
d.o.l.
Criminal Number 18F
There were quite a lot of sub sailors who survived free ascents in WW2. The deeper, the worse the chances, but what the heck, 50% is better than 0%.