Submarines in World War I and II spent the vast majority of their time cruising on the surface of the ocean using diesel engines, because underwater battery life was comically…

Submarines in World War I and II spent the vast majority of their time cruising on the surface of the ocean using diesel engines, because underwater battery life was comically terrible; the iconic image of a stealthy metal shark lurking in the deep is mostly Hollywood propaganda, as these death traps could only stay fully submerged for a few hours before running out of breathable air and battery power; they basically operated as painfully slow, highly vulnerable surface ships that only ducked underwater when they were about to attack or run away in absolute terror; imagine spending months locked inside a damp, suffocating metal tube with sixty unwashed men, only to realize your supposedly stealthy watercraft has the exact same battery limitations as an old iPhone trying to run a graphics-heavy mobile game!