 
        
            The world's first submersible (1620)
            Records show that British carpenter and gunner William Bourne
            designed the world's first truly submersible boat as early as 1578,
            but it was not until Dutch physicist Cornelius Drebbel modified
            Bourne's plans 40 years later that the man-powered submarine finally
            came into existence. Shaped like an enclosed rowboat, the vessel
            included ballast tanks for stability and a system of screws for
            managing the amount of water in her tanks, enabling the submersible
            to sink or rise. Complete with six oars (and 12 oarsmen) for
            propulsion, a snorkel-like apparatus for air, and leather hides for
            waterproofing, Drebbel's third version of this contraption could
            descend to a depth of 15 feet, allowing it to travel down the Thames
            River.