U-2540 Type XXI
Revell (Cutaway)

This subject is out of my comfort zone so I think everybody should do it!

Type XXI U-boats, also known as "Elektroboote" [German: "Electric boat"], were a class of German diesel-electric submarines designed during the Second World War. They were the first submarines designed to operate primarily submerged, rather than as surface ships that could submerge as a means to escape detection or launch an attack. The submarines were rushed into production prematurely, and all of those built suffered from significant defects. As a result, only four of the submarines were completed during the war. The design proved influential, however, with other navies adopting features pioneered in the Type XXI following the Second World War.