The ''U-Flak'' Boat was a type of World War II German Kriegsmarine (Navy) Ship, designed to maximize the usage of damaged U-Boats (Submarines). Their deployment began in mid-1942 and were birst used in The Bay of Biscay (between France and Spain), which was held by German Forces. When a U-Boat was severely damaged to a point that repairing it for ''submersible'' warfare was deemed too expensive – and rather than scrapping or ''gutting'' The Ship for parts was found impractical, such Vessels were converted into ''U-Flak'' Boats.
Refitted as a surface-type ''Patrol Ship'', The ''U-Boat'' had heavy Deck Guns (Flak) Anti-Aircraft rated – installed on it's Deck. These were elevated platforms onto which was fitted 37mm (Quad) Cannon. The Gun platforms were fully traversing (360-degrees) and had 90-degree elevation abilities. Larger U-Boats could have several (2) such platforms on their Decks (Fore and Aft). Attempts where made to install various Rocket Launching platforms, by which to engage small Enemy Cruisers, but such develops were deemed impractical. The U-Flaks Ships still were deployed with their primary weapon, The Torpedo. However, they were ''fixed'' or pre-loaded and could only be fired once (normally 4 Torpedoes). Reloading was accomplished in Port.
The U-Flaks were somewhat effective in their ''new'' role, but still were prey to Destroyers and Battleships, due to their inability to submerge. Likewise, they were open to Enemy Submarine attack as well.