Cruising depth. WWII submarines spend the majority of their time at sea on the surface and only dive during an attack, since their diesel engines need air to function. It wasn't until the advent of nuclear submarines that you'll see them almost always submerged.
actually the germans came up with the systems in use nowadays to allow subs to remain mostly submerged at decent depth but like most of the cool stuff they made it came way to late to have practical effect on the war.
only were able to make a handful of subs with this and out of those only like 2 managed to enter active service the rest were captured after the german surrender and were promptly taken apart for study.
actually the germans came up with the systems in use nowadays to allow subs to remain mostly submerged at decent depth but like most of the cool stuff they made it came way to late to have practical effect on the war.
only were able to make a handful of subs with this and out of those only like 2 managed to enter active service the rest were captured after the german surrender and were promptly taken apart for study.
The Dutch came up with it first. The Germans stole the design when they captured two O-21 series subs after they defeated the Netherlands.
(Okay, technically, a Scotsman came up with the first [documented] design, but the development cycles are unrelated.)