Submarine Volkhov is seen before diving into the water in St. Petersburg, Russia, Dec. 26, 2019. Volkhov, built for Russian Pacific Fleet by Admiralty Shipyard, dived into the water in St. Petersburg on Thursday. (Photo: Irina Motina/Xinhua)

Submarine Volkhov is seen before diving into the water in St. Petersburg, Russia, Dec. 26, 2019. Volkhov, built for Russian Pacific Fleet by Admiralty Shipyard, dived into the water in St. Petersburg on Thursday.

Submarine Volkhov is seen before diving into the water in St. Petersburg, Russia, Dec. 26, 2019. Volkhov, built for Russian Pacific Fleet by Admiralty Shipyard, dived into the water in St. Petersburg on Thursday.

Submarine Volkhov is seen before diving into the water in St. Petersburg, Russia, Dec. 26, 2019. Volkhov, built for Russian Pacific Fleet by Admiralty Shipyard, dived into the water in St. Petersburg on Thursday.

The diving ceremony of the submarine Volkhov is held in St. Petersburg, Russia, Dec. 26, 2019. Volkhov, built for Russian Pacific Fleet by Admiralty Shipyard, dived into the water in St. Petersburg on Thursday.

The diving ceremony of the submarine Volkhov is held in St. Petersburg, Russia, Dec. 26, 2019. Volkhov, built for Russian Pacific Fleet by Admiralty Shipyard, dived into the water in St. Petersburg on Thursday.

Submarine Volkhov is seen before diving into the water in St. Petersburg, Russia, Dec. 26, 2019. Volkhov, built for Russian Pacific Fleet by Admiralty Shipyard, dived into the water in St. Petersburg on Thursday.