The submarine cruiser is taking part in a strategic command-and-staff exercise underway in the Russian armed forces.
Vladimir Putin is expected to stay on the cruiser until tomorrow afternoon.
This is the second time Putin has been at sea on a submarine. In April 2000 he took part in Northern Fleet exercises in the Barents Sea.
On April 5 Putin went to sea aboard the nuclear-powered missile carrier "Karelia" of the Northern Fleet. Following the night on board, over 50 meters under sea level, Putin watched the exercise.
While on the submarine cruiser, Putin "thoroughly familiarized himself" with every compartment, including the one housing the nuclear power plant. The president also examined the submarine's missile launch system.
Moreover, Putin has become a submariner. Ritually, one must drink some seawater, which Putin did to get a certificate of an honorable submariner.
