French submarine Diamant (1933)

The French submarine Diamant was a Saphir-class submarine built for the French Navy in the mid-1930s. Laid down in July 1930, it was launched in May 1933 and commissioned in June 1934. Diamant was scuttled at Toulon on 27 November 1942 to prevent her capture by German forces, then refloated by Italian forces on 29 March 1943. On 22 June 1944, Diamant was bombed and sunk at Toulon by Allied aircraft.

Design
66 m long, with a beam of 7.1 m and a draught of 4.3 m, Saphir-class submarines could dive up to 80 m. The submarine had a surfaced displacement of 761 LT and a submerged displacement of 925 LT. Propulsion while surfaced was provided by two 1300 hp Normand-Vickers diesel motors and while submerged two 1100 hp electric motors. The submarines electrical propulsion allowed it to attain speeds of 9 kn while submerged. Their surfaced range was 7000 nmi at 7.5 kn, and 4000 nmi at 12 kn, with a submerged range of 80 nmi at 4 kn.

The Saphir-class submarines were constructed to be able to launch torpedoes and lay mines without surfacing. The moored contact mines they used contained 220 kg of TNT and operated at up to 200 m of depth. They were attached to the submarine's exterior under a hydrodynamic protection and were jettisoned with compressed air. The Saphir-class submarines also featured an automatic depth regulator that automatically flooded ballast tanks after mines were dropped to prevent the risk of the submarine surfacing in the middle of enemy waters.