Ships in class: Surcouf
At 4,000 tons (3,600 tonnes) displacement submerged, Surcouf was the largest submarine in the world at the start of World War II.
Surcouf was designed as an "underwater cruiser", intended to seek and engage in surface combat. At carried an observation float plane in a hangar built into the after part of the conning tower and was armed with not only 12 torpedo tubes but also a twin 8-inch (200 mm) gun turret forward of the conning tower. The guns were fed from a magazine holding 60 rounds and controlled by a director with a 16 ft 6 in (5.03 m) rangefinder, mounted high enough to view a 7 mi (11 km) horizon. In theory, the observation plane could direct fire out to the guns' 15 mi (24 km) maximum range. Anti-aircraft cannons and machine guns were mounted on the top of the hangar. The design was plagued by many mechanical and operational problems.