Sinking of USS Housatonic The Sinking of USS " Housatonic " on 17 February 1864 during the American Civil War was an important turning point in naval warfare . The Confederate States Navy submarine , " H . L . Hunley " made her first and only attack on a Union Navy warship when she staged a clandestine night attack on the in Charleston harbor . The " Hunley " approached just under the surface , avoiding detection until the last moments , then embedded and remotely detonated a spar torpedo that rapidly sank the 1 , 260 ton sloop - of - war with the loss of five Union sailors . Although the victory was Pyrrhic and short - lived , since the " Hunley " herself was sunk during the attack with the loss of all eight Confederate crewmen , the H . L . Hunley became renowned as the first submarine to successfully sink an enemy vessel in combat and the direct progenitor of what would eventually become international submarine warfare . Sinking . On the evening of 17 February 1864 , the " Hunley " made her first mission against an enemy vessel during the American Civil War . Armed with a spar torpedo , mounted to a rod extending out from her bow , the " Hunley " s mission was to lift the blockade of Charleston , South Carolina by destroying the sloop - of - war USS " Housatonic " in Charleston Harbor . " Housatonic " was a 1 , 240 ton vessel with an armament of twelve large cannon s , stationed at the entrance of Charleston Harbor roughly five miles off the coast . " Housatonic " was commanded by Captain Charles W . Pickering and had a crew of 150 men . The " Hunley " began her approach at about 8 : 45 pm , commanded by First Lieutenant George E . Dixon and crewed by seven volunteers . Accounts differ about the initial approach ; what is known is that the " Hunley " was spotted just before embedding her torpedo into " Housatonic " s hull . Official accounts say " Housatonic " was unable to fire a broadside at " Hunley " , and hit her with only small arms fire . The " Hunley " attached her explosive to " Housatonic " s side before reversing and setting a course for home . A few moments later the torpedo detonated and sank the sloop - of - war . First - hand reports say no explosion was heard by the crew of " Housatonic " , who immediately began climbing the rigging or entering life boat s as the sloop began to sink . Within five minutes , " Housatonic " was partially underwater . " Hunley " thus achieved the first sinking of a warship in combat via submarine . Aftermath . Five men , two officers and three crewmen , went down with their ship while an unknown number of Union Navy sailors were injured . The survivors were later rescued by other elements of the Charleston blockading force . " Hunley " won her first victory , but was lost at sea the same night while returning home to Sullivan ' s Island . It was originally thought that the " Hunley " was sunk as the result of her own torpedo exploding , but some claim that she survived as long as an hour after destroying the " Housatonic " . Support for the argument of " Hunley " s brief survival is a report by the commander of Fort Moultrie on Sullivan ' s Island that prearranged signals from the sub were observed , and answered ; he did not say what the signal was . Further support comes from the testimony of a lookout on the sunken " Housatonic " , who reported seeing a " blue light " from his perch in the sunken ship ' s rigging . There was also a post - war claim that two " blue lights " were the prearranged signal between the sub and Fort Moultrie . " Blue light " at the time of the Civil War was a pyrotechnic signal in long use by the US Navy . Modern claims in published literature on the " Hunley " have repeatedly and mistakenly been that the " blue light " was a blue lantern , when in fact no blue lantern was found on the recovered Hunley , and period dictionaries and military manuals confirm the 1864 use and meaning of " blue light . " This was the last time the " Hunley " was heard from , until her recovery from the waters off Charleston , SC . While returning to her naval station Hunley sank for unknown reasons . However , a team of historians managed to examine the submarine ' s remains , and theorized that a crewman on the " Housatonic " was able to fire a rifle round into one of the " Hunley " ' s viewing ports . A film entitled " The Hunley " was made about the story of " H . L . Hunley " and the sinking of " H . L . Hunley " . New evidence announced by archaeologists in 2013 indicates that the " Hunley " may have been much closer to the point of detonation that previously realized , thus damaging the submarine as well .