David Bushnell

David Bushnell (1754–1824), of Westbrook, Connecticut, was an American inventor and a veteran of the Revolutionary War. He is credited with creating the first submarine ever used in combat, while studying at Yale College in 1775. He called it the Turtle because of its look in the water. His idea of using water as ballast for submerging and raising his submarine is still in use, as is the screw propeller, which was used in the Turtle.