That's very interesting sounding. The raisable thingy. Sounds cool.
The IIA's crush depth is 150m I believe. Safely, I go down to 130m during those nasty destroyer attacks. So long as your hull hasn't been damaged, you'll be fine at 130m as far as I know, but if you get that uncomfortable just go to 100m instead.
The IID's crush depth is 175m??? I forget, but I can go down to 150m safely in that boat. ^^
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Yes. I know type II U-Boats aren't good, but I like them anyway. Why? I'm just different like that. I always have liked smaller things. It's kind of like light tanks if you know what I mean.

And when in doubt, YIIIIIIIIAAAAAAAAAUUUUUUUHHH!!!!!!!!!!

Also, I fight for my friends!