Horace Lawson Hunley
Horace L. Hunley was a lawyer and a member of the Louisiana state legislature who had a thing for submarines. He helped design and build three different models for the Confederacy during the Civil War and was ultimately killed when his third design went under. His first submarine was built in New Orleans and was intentionally sunk when the city fell to the Union in 1862, and his second submarine sunk in Mobile Bay in Alabama. Hunley funded his third submarine himself, and on Oct. 15, 1863, Hunley, along with seven crewmembers, died when the sub that carried his name (depicted in a painting here) sank in the waters off Charleston, South Carolina.
The Confederacy recovered the sunken sub and sent it back out with a new crew who managed to stay alive and also managed a major accomplishment: to sink a ship. It was the first ship to be taken down by a submersible vessel. However, the Hunley disappeared on this first and last successful mission, taking its third crew to the bottom of the sea.