Right? I always think of submarines as small and cramped, and while they are certainly cramped, they're not generally small. Lot of machinery goes into those beasts.
One of the key events that gave the United States the politically-charged push into the war was the sinking of the Lusitania, and it was done by a German u-boat.
Here's another weird one you didn't expect: Germans used zeppelins to bomb London.