The U boat was designed, developed and manufactured during WWI the U boats on their own sank over 5000 ships and killed over 15,000 people which many of were innocent due to the targeting of merchant ships. U boats caused so much problems that merchant ships had to be escorted by 10+ warships and extra liberty ships this in-turn cause more sinking due to the being no way to counter them at the time --appearance-- the u boats varied in appearance due to them being different in shape size and color but they typically looked like a covered up destroyer and sometimes there decks did not have armor
=the only surviving type XXI U-boat=
=here's another view of the U-boat=

--instructions-- VTOL for submerging and surfacing the U-boat trim is for aiming the cannon up and down actv1:front cannon actv2:back cannons --personal note-- this is my second submarine and I built just after the Thresher