1-151-929 - Ann Ronan Picture Library/Heritage-Images

'Turtle', submarine designed by David Bushnell, 1787. Bushnell (1742-1824) built the Turtle, the first American submarine, in 1776. The Turtle was powered by a propeller operated by its single occupant turning a handle and would normally float with approximately six inches of exposed surface. The volume of air in the vessel was sufficient for it to remain submerged for up to 30 minutes. Several unsuccessful attempts were made to use the Turtle to deliver and attach underwater bombs to British warships during the American War of Independence.