Submarines can stand water pressure thanks to their shape. As submarines are roughly ovoidal or "rounded", pressure is equally distributed on their whole surface. In a few words, an object having a round shape stands much more pressure than a squared one. But of course a submarine cannot go deeper and deeper. There is a limit that also a submarine must respect to avoide being smashed. The material does not really make the difference. In fact there are fishes that live in the dark depths. How can they survive?
The research leading to these results has received funding from the European Community´s Seventh Framework Programme (FP7/2007-2013) under Grant agreement n. 217766 