I was reading this article... Here's what they said about decks awash:
"If the center of gravity and the center of buoyancy are coincident and if a wave were to hit the boat from the side, capsizing could occur. Those Hollywood movies where a submarine is shown with decks awash, making an approach on the surface is mostly fiction. That is about where the two centers become coincident and it doesn't take much to roll the boat over."
Apparently (according to this article) they never used decks awash in WWII.
Can someone confirm? (Or refute.)
The article in question:
http://www.subvetpaul.com/Flt_Class_Sub.html