On 12 April 1963,
K-33 collided with the
Finnish merchant vessel in the
Kattegat.
Finnclipper, owned by
Enso Gutzeit, was on her way to the
United States with a load of 6,000 tons of paper. When she reached the Kattegat, there was a mist.
Finnclippers crew heard engine noise on their
port side at 11.05 a.m. and a submarine emerged from the mist.
Finnclipper steered sharply to
starboard to try to avoid a collision, but to no avail.
Finnclipper immediately stopped and returned to the submarine to see if she needed help. Two Soviet officers on board told the Finnish captain that the submarine's side had suffered severe structural damage, having been pressed in and deformed. The Soviet officers did not reveal their nationality, but told
Finnclippers crew that their vessel was a
Warsaw Pact submarine. The Finns, however, could read the number 921 clearly on the side of the submarine, identifying her as
K-33. According to some Soviet sources,
K-33 underwent an
overhaul at a Soviet
Northern Fleet base from 25 October 1962 through 29 December 1964 and therefore could not have been involved in the collision, and at the time the Soviets claimed that the submarine involved was not a
nuclear submarine, although
Finnclippers crew had identified
K-33 clearly. A 1996 Russian article says
K-33 was en route to a patrol in the North
Atlantic Ocean when she collided with
Finnclipper.
Finnclipper managed to cross the Atlantic Ocean after the collision, although she had sprung a leak. The severely damaged
K-33 limped to
Murmansk for repairs. The
captain of the Finnish vessel, Runar Lindholm, gave a
maritime declaration when arriving in
New York, but the report was labeled "secret" for over 44 years. It has been speculated that the incident was held secret due to the
Finno-Soviet Treaty of 1948, under which the Soviets could forbid the Finns to report the incident in the news media or even to research it. On 4 April 2007, Lindholm and maritime author Jaakko Varimaa, who at the time was
second mate on
Finnclipper, published the book
Sukellusvene sumussa ("
Submarine In The Mist"), revealing the accident to the general public. ==Arctic incident==