A submarine is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term is also sometimes used historically or colloquially to refer to remotely operated vehicles and robots, as well as medium-sized or smaller vessels, such as the midget submarine and the wet sub. Submarines are referred to as "boats" rather than "ships" irrespective of their size.
The Greater Underwater Propulsion Power Program (GUPPY) was initiated by the United States Navy after World War II to improve the submerged speed, maneuverability, and endurance of its submarines.
The Balao class was a successful design of United States Navy submarine used during World War II, and with 120 boats completed, the largest class of submarines in the United States Navy. An improvement on the earlier Gato class, the boats had slight internal differences. The most significant improvement was the use of thicker, higher yield strength steel in the pressure hull skins and frames, which increased their test depth to 400 feet (120 m). Tang actually achieved a depth of 612 ft (187 m) during a test dive, and exceeded that test depth when taking on water in the forward torpedo room while evading a destroyer.
Tench-class submarines were a type of submarine built for the United States Navy (USN) between 1944 and 1951. They were an improvement over the Gato and Balao classes, only about 35 to 40 tons larger, but more strongly built and with a slightly improved internal layout. One of the ballast tanks was converted to carry fuel, increasing range from 11,000 nautical miles to 16,000 nautical miles. This improvement was also made on some boats of the previous two classes. Further improvements were made beginning with SS-435, which are sometimes referred to as the Corsair class. Initial plans called for 80 to be built, but 51 were cancelled in 1944 and 1945 when it became apparent that they would not be needed to defeat Japan. The remaining 29 were commissioned between October 1944 (Tench) and February 1951 (Grenadier). The last submarine of the Tench class, as well as the last submarine which served during World War II, remaining in service with the U.S. Navy was USS Tigrone (AGSS-419) which was decommissioned on 27 June 1975.
Minerve was a diesel–electric submarine in the French Navy, launched in 1961. The vessel was one of 11 of the Daphné class. In January 1968, Minerve was lost with all hands in bad weather while returning to her home port of Toulon.
Farfadet (Q7) was an early submarine built for the French Navy at the beginning of the 20th century. She was of the Maugas type, and the name ship of her class. Farfadet accidentally sank in July 1905 at Bizerte with the loss of 14 men of her crew; two men survived. She was later refloated and recommissioned as the Follet (Q7). She was stricken in November 1913.
The Redoutable-class submarines were a group of 31 submarines built between 1924 and 1937 for the French Navy. Most of the class saw service during the Second World War. The class is also known in French as the Classe 1 500 tonnes, and they were designated as "First Class submarines", or "large submarine cruisers". They are known as the Redoutable class in reference to the lead boat Redoutable, in service from 1931 to 1942. The class is divided into two sub-class series, Type I, known as Le Redoutable and Type II, Pascal.
The Submarine Forces of France are one of the four main components of the French Navy. The force oversees all French submarines regardless of role.
Espadon was a Narval-class submarine of the French Navy. Along with sister boat Marsouin, the boat was the first French submarine to steam under sea ice. The boat is currently a museum ship.
The Brumaire-class submarines were built for the French Navy prior to World War I. There were sixteen vessels in this class, of the Laubeuf type.
French submarine Narval (“Narwhal”) was a pioneering vessel of the French Navy, designed by Maxime Laubeuf and built at the end of the 19th century. She was designed in response to a competition set by the French Admiralty and had several revolutionary features which set the pattern for submarines for the next 50 years.
Redoutable was the lead ship of the Redoutable-class submarines of the French Navy launched in 1928 at Cherbourg, France. It participated in the Second World War, first on the side of the Allies from 1939 to 1940, then on the side of the Axis for the rest of the war. She was scuttled by the French on 27 November 1942 to prevent her capture by the Germans during their advance on Toulon, but was then refloated by the Italians in 1943. On 11 March 1944 she was sunk by bombs from Allied aircraft.
Three submarines of the French Navy have borne the name Espadon :
The Requin-class submarines were a class of nine diesel-electric attack submarines built for the French Navy in the mid-1920s. Most saw action during World War II for the Vichy French Navy or the Free French Naval Forces. Nine ships of this type were built in the shipyards of Brest, Cherbourg and Toulon between 1923 and 1928. The class was part of the French Marine Nationale, serving in the Mediterranean Sea. All member ships took part in World War II, fighting on both sides of the conflict; Four were captured by Italian forces and sunk by the Allies. Only one ship survived the war - Marsouin, decommissioned shortly after the war's end.
The French submarine Dauphin was a Reqin -class submarine built for the French Navy in the mid-1920s. Laid down in December 1922, it was launched in April 1925 and commissioned in November 1927. It was captured by Italian forces on 8 December 1942 and renamed FR 115. It was later recaptured by the Germans on 9 September 1943, then scuttled on 15 September 1943. The name Dauphin comes from the French word for Dolphin.
The French submarine Espadon was a Requin-class submarine built for the French Navy in the mid-1920s. Laid down in October 1923, it was launched in May 1926 and commissioned in December 1927. It was disarmed at Bizerte, Tunisia in April 1941 and captured there by Italian forces on 8 December 1942 and renamed FR 114. It was scuttled by the Italians at the Castellamare shipyard on 13 September 1943, then raised by the Germans in 1943 but not repaired.
The French submarine Narval was a Requin-class submarine built for the French Navy in the mid-1920s. Laid down in March 1923, it was launched in May 1925 and commissioned in July 1926. It joined the Free French naval forces at Malta at the time of the French surrender during World War II. On or around 15 December 1940, Narval sank after striking a mine in the same minefield off the Kerkennah Islands that sank her sister ship Morse six months prior.
Phoque was a Requin-class submarine built for the French Navy in the mid-1920s. Laid down in May 1924, it was launched in March 1926 and commissioned in May 1928. In April 1941, it was disarmed at Bizerte, Tunisia and captured there by the Italians on 8 December 1942 and renamed FR 111. It was sunk on 28 February 1943 10 miles off Murro di Porco, Sicily by Allied aircraft.
Three submarines of the French Navy have borne the name Dauphin:
Marine Nationale 
