What was the name of the Soviet submarine that reached a depth of about 1,027 metres in 1985?

K-278 Komsomolets reached a depth of about 1,027 metres in 1985.

K-278 was a Soviet nuclear-powered attack submarine and the only completed Project 685 Plavnik boat. Its titanium pressure hull gave it exceptional strength, allowing it to dive far deeper than most operational military submarines.

The submarine set its record depth on 4 August 1985. K-278 later entered service under the name Komsomolets, meaning “member of the Young Communist League.” It was designed as an experimental platform as well as an attack submarine.

Komsomolets was lost to fire in the Norwegian Sea on 7 April 1989. Forty-two crew members died, and the wreck remains on the seabed. Its record is often confused with speed records set by other Soviet submarines, especially the titanium-hulled Alfa class.