French submarine Turquoise (1929)

The French submarine Turquoise was a Saphir-class submarine built for the French Navy in the mid-1930s. Laid down in October 1926, it was launched in May 1929 and commissioned in September 1930. Turquoise was disarmed at Bizerte, Tunisia and renamed FR 116 after being captured there by Italian forces on 8 December 1942. Turquoise was recaptured and scuttled by German forces at Naples, Italy on 8 May 1943.

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.