The hull of the first submarine in history to sink an enemy warship has been cleaned and revealed for the first time in 150 years.
After a year of painstaking work, scientists using small chisels and hand tools have removed encrusted sand, sediment and rust from the outside of the hand-cranked Confederate submarine H.L. Hunley.
Now, the outside appears much as it did when the Hunley and its eight-man crew rammed a spar with a powder charge into the USS Housatonic and sank the Union blockade ship off South Carolina in 1864.
But scientists said Thursday that cleaning the hull didn't solve the mystery of why the Hunley itself sank with its crew before returning from its mission.
Cleaning the hull showed some dents on both sides of the submarine.
But scientists say it's not clear when the dents occurred. The Hunley sank twice before it went on its 1864 mission, though it also could have been dented at the time of the Housatonic attack or later when the sub sat for decades on the ocean floor off Charleston.
"If there was a smoking gun, we would have seen it a long time ago," said Johanna Rivera-Diaz, a conservator with the Hunley project.