For the first time since the U.S. Civil War, the Confederate vessel H.L. Hunley—the world's first submarine to sink an enemy ship—was revealed on January 12 (pictured) after 11 years of conservation work.

Shown in a South Carolina conservation facility, the Hunley sank the U.S.S. Housatonic off Charleston (map) in 1864. Within minutes the sub itself sank too-killing its eight-man crew and creating an enduring mystery.

with spar torpedo packed with explosive powder and attached to a long pole on its bow. The spar torpedo embedded in the sloop's wooden side was detonated by a rope as Hunley backed away. The resulting explosion that sent Housatonic with five crew members to the bottom of Charleston Harbor also sank Hunley with its crew of eight. H.L. Hunley earned a place in the history of undersea warfare as the first submarine to sink a ship in wartime.

Naval engineers still marvel at the Hunley's design and construction. For example, the ship's knifelike, rolled-iron hull and recessed rivets helped reduce drag as the sub cut through the water.

Driven by 136 years of chemical reactions between salt water and the Hunley's iron hull, concretions lend a rough appearance to the rear hatch (pictured with its cap removed) and to much of the rest of the Civil War submarine.

The concretions will provide valuable information about what happened to the submarine after it had sunk in 1864, according to archaeologist Maria Jacobsen. Already the concretions suggest that natural forces alternately covered and uncovered the sunken Hunley with silt.

The 40-foot-long (12-meter-long) Hunley had two ballast tanks—one front, one rear—which could be filled with water to submerge the submarine. Crewmen manually pumped out the water to rise again.

At only about 4 feet (122 centimeters) tall and 2 feet (61 centimeters) wide, the interior of the Hunley was so cramped that its eight crewmen couldn't trade places after they'd taken their stations. (See "Hunley Findings Put Faces on Civil War Submarine.")

During a mission, seven men sat on a long-gone wooden bench on one side of the craft and turned a crankshaft (visible above) to power the Hunley's propeller.

The handles on the crankshaft were arranged in a staggered fashion, so that all crewmen weren't applying maximum force at the same times. The arrangement kept the propeller turning smoothly and kept the Hunley from lurching.

The eighth crewmember was the submarine's commander, who stood at a small conning tower with small glass windows at the front of the Hunley. The commander steered the sub via a rudder and controlled horizontal fins that helped the Hunley dive and surface.

The Hunley's crankshaft operators (such as this one shown in a diagram) entered one by one and crawled or duck-walked through the submarine to take their positions. The commander was the last to enter.

When the submarine was recovered and opened in 2000, archaeologists discovered that the eight crewmen had died at their stations. There was no indication that the crewmen had tried to escape.

Archaeologists think the men passed out and eventually suffocated as the air inside the submarine was used up.