Type U 23s had an
overall length of The boats'
beam was , the
draught was . The boats
displaced when surfaced and when submerged. Type U 23s were fitted with two
Germaniawerft 6-cylinder two-stroke
diesel engines with a total of for use on the surface and two
SSW double-acting
electric motors with a total of for underwater use. These engines powered two shafts, which gave the boats a top surface speed of , and when submerged. Cruising range was at on the surface and at submerged. Constructional diving depth was . The U-boats were armed with four
torpedo tubes, two fitted in the
bow and two in the
stern, and carried six
torpedoes. All boats received one
SK L/30 deck gun. The boats'
complement was 4 officers and 31 enlisted. == Ships ==