I've sunk like a brick as well but there is another part to this problem is that if you sink to the sea floor no matter how shallow you sub seems to crush itself to death. I took out a balao and rammed it into some hawaiian island to see if I could replicate the problem and sure enough my forward torpedo room flooded and as soon as I touched bottom everything else started to take a crap. you can sit on the bottom but if you sink to the bottom because of flooding it's all over.