Whats the fastest submarine

K-222 was laid down on December 28, 1963 and commissioned on December 31, 1969, at Severodvinsk. She was assigned to the Soviet Red Banner Northern Fleet for the duration of her career. She was the world's fastest submarine, reaching a record submerged speed of 44.7 kn (51.4 mph; 82.8 km/h) on trials.