U-boat SC 305 was first located last autumn with the help of advanced sonar. But only now has its identity been confirmed.
"We are 8 private individuals who have been looking for this submarine completely voluntarily - and we found it," said Björn Rosenlöf, one of the team.
"The whole thing began when one of the team found details in the Finnish war archive about where this U-boat was sunk by a Finnish submarine."
The wreck was discovered in deep waters outside Grisslehamn, between Åland and Sweden.
"Then the winter came so we couldn't go out and film it to confirm the identity," said Rosenlöf.
In June another dive was carried out with the help of a remote controlled underwater camera.
"We have managed to identify the vessel. We have found numbers and letters in brass on the tower, so we know with 100 percent certainty that it is the right boat," said Rosenlöf.
Trawling the Finnish archives, the team found themselves on the track of a spectacular drama on the high seas.
On the day of 5th November 1942, the Russian submarine fired upon a convoy between Åland and Sweden but missed its target.
A Finnish U-boat under the command of captain Anti Leino was dispatched from Mariehamn. During the night, Leino found the Russian boat.
The two submarines were at the sea's surface when the Finnish vessel fired two torpedoes. Both missed, and when the Russian sub tried to escape with a rapid dive, Captain Leino decided to ram his enemy.
"It's an unbelievable situation and an extraordinary feat from the Finnish captain to make this split-second decision in the heat of battle, putting his and his crew's life at risk," said Björn Rosenlöf.
The Russian submarine sank with a crew of 38 men onboard. Meanwhile, the Finnish boat limped back to Mariehamn, damaged and offloading water with pumps.
Since the site of SC 305 is a war grave, the search team has chosen not to reveal its exact location. All information and documentation was handed into the Swedish military on Tuesday morning and navy officials will now decide what is to become of the site.
"We have no financial interest in this. It's a hobby, as simple as that," said Rosenlöf.