[mookiemookie]

Were you damaged previously? Any kind of prior hull damage can seriously limit your ability to dive deep without being crushed. SH4 doesn't, at present, give you a hull damage percentage number like SH3 does. If you see spraying water in your conning tower or control room, you'll know you have hull damage.

And of course, you didn't hit bottom, did you?

Also, remember that Japanese ASW was not very good at the beginning of the war. Funny thing about SH4...sometimes you'll get a destroyer crew full of idiots, and sometimes you'll get the devil. You never can tell.