Graduated from Yale in 1775, at the outbreak of the American Revolution, he went to Saybrook, where he built a unique turtle-shaped vessel designed to be propelled under water by an operator who turned its propeller by hand. The craft was armed with a mine, or a torpedo, to be attached to the hull of an enemy ship. Several attempts were made with Bushnell's “Turtle” against British warships. Though the submarine gave proof of underwater capability, the attacks were failures, partly because Bushnell's physical frailty made it almost impossible for him to perform in person the many demanding functions required to control the craft. Gen. George Washington, however, gave him a commission in the engineers, where he rose to captain and command of the U.S. Army Corps of Engineers stationed at West Point. In his later years he studied medicine and entered practice in Warrenton.