Rust still is the biggest problem for ships and everything that is permanently in contact with seawater. See Queen Mary´s ship propeller. It is is made from stainless steel and it starts to rust. It´s just skin deep but it shows how agressiv seawater is. I would like to test a normal steel divers watch and a sub steel U by fixing them under a supertanker for 1 year and see the difference. Any volunteers here? :-D Or somebody here with a supertanker?
Of course this is not representative to show how good sub steel is, but if they use it on German submarines it gives me a better feeling when I am bathing in the sea. Even on a Rolex they tell you that you should clean it with freshwater after using it in the sea, I guess they know why. This leads to the insight that sub-steel is definitive no PR gimmick!
Sorry for not wearing my U on QM II. It´s my Citizen Promaster Titanium but Titan is still better than normal stainless steel.
So here are some pictures