What is a U-Boat?

You've heard the term U-boat when speaking of German submarines during World War II. But what is a U-boat? This military term refers to submarine boats with external, high-arched hulls that enable them to submerge and resurface quickly, like sharks. However, unlike the sleek, streamlined U.S. Navy submarines of today which resemble the jellyfish shapes you see in aquariums, these early submarines had long narrow bodies and were designed for speed rather than stealth. The first was built by Simon Lake for the U.S.