SM U-88 was a Type U 87 submarine built for the Imperial German Navy (Kaiserliche Marine) in World War I. U-88 was engaged in the naval warfare and took part in the First Battle of the Atlantic.U-88 is most notable for sinking and taking with her Kapitänleutnant Walther Schwieger, responsible for sinking the RMS Lusitania when he was commander of 'U-20.