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.