5. Nautilus
This was another invention by an American after the Turtle and was the first metal submarine ever built. America’s Robert Fulton designed the Nautilus in 1800 while working for the French government. Nautilus was a 21-foot undersea featuring multiple groundbreaking innovations. Its hull took the shape of a cigar. It had a copper conning tower and used a hand-driven, four-bladed propeller for underwater movement. For its surface travel, the vessel featured a fan sail and collapsible mast on its rear. It had diving planes used to submerge it and copper bottles filled with compressed oxygen for the crew. After it had failed to win both the French and the English navies, Nautilus was dismantled and sold for scrap.