Death could have been instantaneous, and I hope it was. Or death could have been slow and agonizing, as the sailors waited to suffocate at their stations (the only place they could sit down).
The second sinking was different. Nose down with valve open, the stern would have an air bubble as the sub filled up. You would expect everyone crowded aft.
Maneuvering past that crank must have been quite an obstacle course. I've always assumed the center bench position was FILO...
For completeness: in the first sinking (partial crew, alongside [?Ft. Johnson?] dock, both hatches open, swamped by wake of passing vessel) bodies were clustered around both hatches. IIRC, one crewman [?Haskell?] escaped via the front conning tower, but the hatch trapped his leg and dragged him down quite a ways, before he finally freed himself...
Assuming those hatch covers are about 1.5 sq ft in area, that means that every foot of submersion adds about 100 lbs of force required to open one of them...