The First Submarine
The "Turtle" was the first verified submarine capable of independent underwater operation and movement, and the first to use screws for propulsion. It was also the first military submarine as it was designed during the American Revolutionary War and meant to drill into a ship's hull and plant a keg of powder, which would be detonated by a time fuse.
Turtle was invented in Connecticut in 1775 by David Bushnell. Named for its shape, Turtle resembled a large clam as much as a turtle; it was 7.5 feet (2.3 m) long, 6 feet (1.8 m) tall, and about 3 feet (0.9 m) wide, consisting of two wooden shells covered with tar. It submerged by allowing water into the hull and ascended by pushing water out through a hand pump, similarly to the use of ballast tanks in modern submarines, and was propelled vertically and horizontally by hand-cranked propellers, the first recorded use of the screw propeller for ships. It was manned and operated by only one person.