The David, a semi-submersible built in 1862 under the aegis of a desperate Confederate States of America, is most remarkable for its repeated and quiet failures. It was fifty feet long.
It is not considered a true submarine because part of its boiler protruded above the surface. It used open ballast tanks to maintain depth and attacked with a "spar torpedo"--a 134-pound explosive charge mounted on the end of a metal pole.
The two people responsible for the David were Theodore Stoney and Julian Ravenel, both private citizens. They built the body from salvaged wood and metal; the boiler came from a train. The name David, given in earnest by Ravenel's wife, reflects the impossible gap between Confederate and Federal submersible technology.
The USS New Ironsides, David's first target, was equipped with fourteen smooth-bore cannons and was considered the world's most formidable watercraft. On the moonless night of October 5, 1863, the CSS David crawled through the Federal blockade outside Charleston Harbor; after being hailed fifty yards from target, the David's crew discharged a shotgun and charged. The spar torpedo blew away part of New Ironsides' starboard quarter.
The upthrown water killed the David's boiler, and it floated, absorbing Federal small-arms fire. The assistant engineer returned to the vessel after having abandoned it, revived the fires, and navigated to safety.
The CSS David would never damage another vessel. After delivering three unsuccessful attacks that October, its last known incitement was to attack the frigate USS Wabash in April 1864. Its ultimate fate is unknown.
Martha M. Boltz, The Washington Times. "The CSS David -- In a Class of Its own".
Department of the Navy -- Naval Historical Center. "CSS David".
Wikipedia. "CSS David".