Tango-class

The Tango class, designated Project 641B Som (Catfish) by the Soviet Union, was a class of diesel-electric submarines developed to succeed the Foxtrot class. Produced at Gorky, the first vessel was completed in 1972. A total of 18 submarines were built in two variants, with the later version featuring an increased hull length to accommodate anti-submarine warfare (ASW) missile equipment.

The design utilized the same propulsion plant as the final subgroup of the Foxtrot class but incorporated a higher battery capacity, resulting in increased pressure hull volume. This configuration allowed for underwater endurance exceeding one week without the use of a snorkel. The bow sonar installations were similar to those utilized on Soviet nuclear attack submarines. The hull was finished with a rubber coating, leading to the nickname "rezinka" (rubber). These design characteristics were intended for ambush operations against nuclear submarines at maritime chokepoints.

The Soviet Navy assigned the Tango class to the Northern and Black Sea Fleets. The class entered commission in 1972 and remained in service until 2016. B-380 of the Black Sea Fleet was the final unit decommissioned. Following a period of layup in Sevastopol, B-380 capsized and partially sank in December 2019 when the floating dock PD-16 foundered. Scrapping of the vessel began in May 2020.

Three units of the class are preserved as museum ships. B-307 is located at the AvtoVAZ Technical Museum in Tolyatti, Russia; B-396 is stationed at the Moscow Navy Museum; and B-515 is located in Hamburg, Germany. The conning towers of B-319 and B-474 are on display in Polyarny and Ryazan. Additionally, the sail of B-380 was installed as a monument in the Moscow district in 2021.