Oh, tougher damage modelling is fine, I was just wondering if perhaps my sub was taking hit point damage from the previous collisions (the only way I could see suffering the sudden insta-death that I did) while the target was either A) Sinking based only on buoyancy, as I believe the NSM Mod is or B) sitting in some sort of state whereby it had taken all the damage it was going to take and couldn't be pushed over the edge by anything short of another torpedo or several more shells.
In any event, my save game file from prior to the engagement appears to be corrupt, as it crashes the game on loading, so... the USS S-30 is on the bottom for good, now. Tonight, I must start a new career (and make a new signature)
I wonder what S-Boat I'll get this time? I'd play a Porpoise but I want to earn it