The wreck is believed to be a class S-2 Soviet submarine that sunk after hitting a mine during WWII. The submarine went down in April of 1940 with 50 crewmembers onboard.
The search team, which includes the grandson of a man who witnessed the submarine take its fatal blow, has been searching for the S-2 since 1999.
Finnish and Swedish authorities have yet to determine in whose waters the submarine initially touched the sea bottom.
The group has notified Finnish and Swedish authorities as well as the Russian Embassy in Stockholm of the find.