Type XI.

This is coolbert:

The French had one. The Germans had them too. At least on paper and in the works.

Once more the topic is the cruiser submarine Think a submarine of the class and type Surcouf.

Thanks to the tip from Harry at Sharkhunters.

TYPE XI GERMAN SUBMARINE.

PRIMARY WEAPONRY AS ENVISIONED BIG BORE NAVAL GUNFIRE AND NOT TORPEDOES.

"The Type XI U-boat was planned as an artillery boat; its main armament would have been four 128-mm [5 inch] guns, in two twin gun turrets. It would have also carried an Arado Ar 231 collapsible floatplane. Four boats (U-112, U-113, U-114, and U-115) were laid down in 1939, but cancelled at the outbreak of World War II . . . Its purpose was to engage ships (including escorts) in artillery duels at relatively long range, then dive away if they came within a certain threshold distance. Many anti-submarine escorts of WW2 including the Flower corvettes would have been too small and too poorly equipped with forward guns to cope with this approach."

Type XI a cruiser submarine. A raider I envision the mission of which as similar to the German famous surface raider ships of the Second World War. An Atlantis type warship with a submersible capability.

See at this previous blog entry the deficiencies as associated with the gunnery of the cruiser submarine.

See also additional deficiencies of the cruiser submarine as a submersible warship:

"Large submarines remained vulnerable to damage from Defensively Equipped Merchant Ships (DEMS), were slow to dive if found by aircraft, offered a large sonar echo surface, and were less able to defensively maneuver during depth charge attacks."

coolbert.