In my case I was struck by a Depth charge in the rear and some how survived. I was kind of disapointed at the game when I recieved no dmg reports initially, but after managing to evade the DDs I had to blow ballast when I found myself rapidly sinking to 400 + feet. Amazingly I survied and managed to hit flank speed and speed away before the DDs watch noticed me.
Heres the Depth charge hit >
http://img155.imageshack.us/img155/308/dcik7.jpg
Heres what happened when I was testing my ability to dive again. Notice my props arent moving when my electrics should be kicking in. This may be due to dmg to my electrics or maybe the engines cut after a certain degree change>
http://img155.imageshack.us/img155/3946/pdnj2.jpg
After that test I fell to over 200 feet before managing to become neutral and then ascend.
Going to make the return journey interesting to say the least..
BTW I am still playing on 1.1 due to having lots of mods and not using the mod install tool.. and being lazy