Sounds like a mine - for me, mines always destroy the radio room - that room goes red (often along with the crew) and floods, and the conning tower gets the rest of it. That's because the boat bulges at about radio room, so that's where you tend to brush a mine and set it off. Let me guess - you came out of time compression to find yourself digging into the seabed? 2019's right - there's a strip of mines just west of Calais - there a little blue dip in the seabed - perfect sub hiding place, and it's mined.
Kb
__________________
|