Tench-class submarine

	USS Toro shown post-war, after removal of her deck guns, c. 1947.
Class overview
Builders	Portsmouth Naval Shipyard; Electric Boat Company; Boston Navy Yard;
Operators	United States Navy; Republic of China Navy; Turkish Navy; Hellenic Navy; Peruvian Navy; Pakistan Navy; Royal Canadian Navy; Italian Navy; Brazilian Navy; Bolivarian Navy of Venezuela;
Preceded by	Balao class
Succeeded by	Barracuda class
Subclasses	Corsair class
Built	1944–1951
In commission	1944–present
Completed	29
Canceled	51
Active	1
Lost	1
Retired	27
Preserved	3
General characteristics
Type	Diesel-electric submarine
Displacement	1,570 tons (1,595 t) surfaced; 2,416–2,429 tons (2,455–2468 t) submerged;
Length	311 ft 8 in – 311 ft 9 in (95.0 m)
Beam	27 ft 3 in – 27 ft 4 in (8.3 m)
Draft	17 ft (5.2 m) maximum
Propulsion	4 × diesel engines driving electrical generators (Fairbanks-Morse or General Motors (Corsair only)); 2 × 126-cell Sargo batteries; 2 × low-speed direct drive electric motors (Elliott Company, General Electric, or Westinghouse); two propellers; 5,400 shp (4,000 kW) surfaced; 2,740 shp (2,040 kW) submerged;
Speed	20.25 knots (38 km/h) surfaced; 8.75 knots (16 km/h) submerged;
Range	11,000 nautical miles (20,000 km) surfaced at 10 knots (19 km/h)
Endurance	48 hours at 2 knots (3.7 km/h) submerged; 75 days on patrol;
Test depth	400 ft (120 m)
Complement	10 officers, 71 enlisted
Armament	10 × 21-inch (533 mm) torpedo tubes; (6 forward, 4 aft); 28 torpedoes; 1 × 5-inch (127 mm) / 25 caliber deck gun; Bofors 40 mm and Oerlikon 20 mm cannon;

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 preceding 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 (20,000 km; 13,000 mi) to 16,000 nautical miles (30,000 km; 18,000 mi). 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, and eventually orders were placed for 134 (numbered SS-417 to SS-550), but 105 were cancelled in 1944, 1945 and 1946 when it became apparent that they would not be needed to defeat Japan; a further 12 boats (SS-551 to SS-562) were planned to be ordered in 1945 but orders for these were never placed. Some of these (including numerous units which were cancelled) were allegedly of the Balao design, but official US Navy publications allot all to the Tench class. The remaining 29 were commissioned between October 1944 (USS Tench (SS-417)) and February 1951 (USS Grenadier (SS-525)). 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 the USS Tigrone (AGSS-419) which was decommissioned on 27 June 1975.

One Tench-class submarine is reportedly still in active service, USS Cutlass (SS-473), which was transferred to the Republic of China Navy in 1973. ROCS Hai Shih (S 791) is expected to remain in service until 2026, 82 years after she was first launched in 1944.

Three Tench-class boats survive as museum ships; USS Torsk (SS-423) and USS Requin (SS-481) in the United States, and USS Thornback (SS-418), renamed TCG Uluçalireis (S 338), in Turkey.