The first submarine to sink a warship in combat. She was fashioned from a steam boiler in 1863 and began service for the Confederate States of America on August 7th of that year in the defense of the port of Charleston. Originally, she carried a trailing torpedo, which was quickly abandoned in favor of a torpedo mounted on a spar, designed to be rammed into the hull of a vessel and detonated by means of pulling a rope from a safe distance. The CSS H.L. Hunley sunk twice, killing 12 men, including Horace L. Hunley, the designer of the ship and it's namesake. Each time, she was raised and returned to active duty.
On February 17th, 1864, she encounted the Union sloop-of-war, Housatonic, which she successfully sunk, resulting in the deaths of five sailors. However, the CSS H.L. Hunley never returned from her final mission, and it is speculated that the torpedo blast took her to the bottom as well.