H.L. Hunley, byname Hunley, Confederate submarine that operated (1863–64) during the American Civil War and was the first submarine to sink (1864) an enemy ship, the Union vessel Housatonic.

Hunley The Hunley in a water tank at the Warren Lasch Conservation Center, North Charleston, South Carolina. Mic Smith Photography LLC/Alamy

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The Hunley was designed and built at Mobile, Alabama, and named for its chief financial backer, Horace L. Hunley. Less than 40 feet (12 metres) long, the submarine could hold up to nine crewmen, most of whom propelled the vessel by hand cranking a single screw. Its commander controlled steering and depth. The Hunley was shipped by rail in 1863 to Charleston, South Carolina, where it was launched in July. In practice runs and attempts to attack blockading Union warships, it went to the bottom three times with great loss of life—including that of Hunley himself. Raised one more time, it successfully attacked the Union sloop Housatonic with a spar torpedo on February 17, 1864, sinking the vessel. The Hunley, however, was lost shortly after the attack, along with its eight crewmen.

Hunley Hunley, 19th-century illustration. U.S. Navy

The vessel lay in only 30 feet (9 metres) of water some 4 miles (6 km) offshore until it was found by preservationists in 1995. It was raised intact in 2000 and taken to North Charleston’s Warren Lasch Conservation Center, which had been constructed for the Hunley. The crewmen’s remains were later removed for burial, and the submarine underwent extensive preservation work and research. Of particular interest was the cause of the crew’s death, long thought to be suffocation or drowning. However, when the Hunley was unsealed, the bodies were found at their posts, and there was no indication that the men had tried to evacuate. In addition, the submarine showed no major damage. Various theories were proposed, and in 2017 researchers at Duke University speculated that the blast from the torpedo that sunk the Housatonic produced a shock wave that ruptured blood vessels in the men’s lungs. Known as blast lung, it either killed the crew instantaneously or incapacitated them, causing the Hunley to sink.