SM U-104 was a German Type U 57 U-boat during the First World War. U-104 was built at AG Weser in Bremen, launched on 3 July 1917 and commissioned on 12 August 1917. She completed four patrols under Kptlt. Kurt Bernis and was responsible for the sinking of eight vessels of a total of 10,795 gross register tons (GRT). Among these was the American lightship LV 71, stationed at Diamond Shoals; the latter reported the submarine's presence in the area, at which point Bernis notified the lightship of his intentions and allowed her crew to depart before shelling the vessel and sinking her.