The existence of the submarine was first revealed in 2007, when details about the boat were accidentally published on the Sarov, Nizhny Novgorod region's local government website as part of an account of a meeting with its commander.

[2] It serves in the Russian Navy's Northern Fleet and is being used as a technology demonstrator for testing of upgraded weapons and military equipment or as an intelligence collection boat.

[4] Based on the Kilo-class submarine,[2] it is a unique platform due to the combination of its diesel electric power system and a small nuclear reactor.

[5] It is believed the reactor does not drive the propeller itself, but rather produces electricity to recharge the conventional battery system, greatly extending the underwater endurance of the submarine.

[6][1] On 20 February 2019, Russian Defence Ministry released a video showing the Poseidon unmanned underwater vehicle as it is being launched out of a torpedo compartment aboard Sarov.