The Project 940 Lenok class (a type of Salmon

Salmonidae

Salmonidae is a family of ray-finned fish, the only living family currently placed in the order Salmoniformes. It includes salmon, trout, chars, freshwater whitefishes and graylings...

) (known in the West by its NATO reporting name

NATO reporting name

NATO reporting names are classified code names for military equipment of the Eastern Bloc...

 India class) was a military submarine

Submarine

A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...

 design of the Soviet Union

Soviet Union

The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....

.

The India class of boats were designed for high surface speeds, and had tracks on their hulls so they could operate on the ocean floor. The submarines of this class were designed to function as a base for two Poseidon DSRV

Deep Submergence Rescue Vehicle

A Deep Submergence Rescue Vehicle is a type of Deep Submergence Vehicle used for rescue of downed submarines and clandestine missions. While DSRV is the term most often used by the United States Navy other nations have different designations for their vehicles.- Chinese models :The People's...

's (Deep Submergence Rescue Vehicles), which could rescue the crew of sunken submarines.

While the India class boats have been seen going to the aid of Russian Submarines involved in accidents, they have also been observed working in support of Russian Spetsnaz

Spetsnaz

Spetsnaz, Specnaz tr: Voyska specialnogo naznacheniya; ) is an umbrella term for any special forces in Russian, literally "force of special purpose"...

special operations. The boats had decompression chambers and medical facilities on board. Two vessels of this class were built for the Soviet navy. Both were scrapped in the 1990s.