Soviet submarine K-278 Komsomolets

The K-278 Komsomolets was the Project-685 Plavnik (Russian: проект-685 плавник, meaning "fin", also known by her NATO reporting name of "Mike"-class), nuclear-powered attack submarine of the Soviet Navy; the only submarine of her design class. In the inventory of the Soviet military, K-278 was unique for her submarine depth rating, having reached a depth of 1,020 metres (3,350 feet) in the Norwegian Sea on 4 August 1984.

Source: Wikipedia — Soviet submarine K-278 Komsomolets (CC BY-SA 4.0)