Fifteen years after the Confederate submarine H.L. Hunley was recovered off the South Carolina coast, scientists are finally getting a good look at the hull of the first sub that ever sank an enemy warship.

The Hunley was raised in 2000 with its hull encrusted in hardened sand, silt and rust. Now, after six months of work at a lab in North Charleston, about 70 percent of the gunk on the outside of the hull has been removed.

Conservators say that cleaning the hull should help finally solve the mystery of why the Hunley sank back in 1864 after sinking the Union blockade ship Housatonic.

Senior conservator Paul Mardikian (mahr DEE kee in) says the work has revealed clues but researchers are not ready to discuss them yet.