German submarine U-18 was a Type IIB U-boat of Nazi Germany's Kriegsmarine during World War II. It was laid down 10 July 1935 and commissioned on 4 January 1936. It served in many U-boat flotillas during its service.

German submarine U-24 was a Type IIB U-boat that was in service of Nazi Germany's Kriegsmarine during World War II. She was laid down on 21 April 1936 at the F. Krupp Germaniawerft in Kiel with yard number 554, launched on 24 September and commissioned into the Kriegsmarine on 10 October. Oberleutnant zur See Heinz Buchholz took command on 3 July 1937.