The crash depth can be tweaked, plus, even when you reach it, you dont be destroyed inmediatelly, it depend of the "crash speed" used by the mods you have installed.
If you have a low crash speed, when you pass the crush depth, the sub start to take damage, if the crash speed is low, you will be able to ear cracks and recognize the sub is taking damage, according with the crash speed, it can take many seconds to destroy the sub, and you can blow ballast and recover the ship.
