I nerver heard about this before:
Easter 1963: a marine collision that never saw the light of day
Finnish self-censorship ensured that the incident between a freighter and a Soviet nuclear submarine was hushed up
Good Friday 1963, and in Danish waters in the Baltic Sea the fog was so thick you could hardly see the bow of the boat from the captain's bridge.
Nevertheless, the 6,000-ton Finnish freighter Finnclipper, owned by Enso-Gutzeit and carrying a cargo of newsprint westwards towards the United States, was steaming ahead at 15 knots in contravention of all manner of maritime regulations.
The radar screen did not reveal anything very much, least of all that right ahead of the freighter was a Soviet nuclear submarine convoy. The submarine was escorted front and aft by espionage vessels disguised as fishing trawlers.
http://www.hs.fi/english/article/Eas.../1135226462140