The Hunley was located by Clive Cussler and the National Underwater & Marine Agency, and salvaged by Oceaneering International.
The story about the gold coin carried by Lt. Dixon is true. At the Battle of Shiloh, the gold coin saved his life by blocking a bullet; the dented coin, engraved with the date of the battle, was found in his remains, which had a leg wound.
Since the film was made prior to the recovery of the actual HL Hunley, some details of the ship shown in the film are not accurate. Also, the mock-up which was used for interior scenes was 10% roomier than the actual Hunley. A section of the mock-up can be seen, and entered, at the HL Hunley Restoration site in Charleston, SC.
The U.S.S. Housatonic was the first ship ever sunk by a submarine. The second was the H.M.S. Pathfinder, sunk by the German U-boat, U-21, in the fall of 1914.
Though many details of Lt. Dixon's life and military service are taken from fact, most of the other crew have uncertain identities.