Peter Lindberg, who leads the group, previously
joked to CNN that the first object they found 300 feet below the surface might be an unidentified flying object.
The imaging technique involves pulling a sonar "towfish" -- that essentially looks sideways underwater -- behind a boat, where it creates sound echoes to map the sea floor below.
The team is waiting until the spring to further investigate their intriguing discovery.
"Right now, we know about 20,000 objects, mostly shipwrecks, in the Baltic Sea. But I think there may be more than 100,000," sonar expert Ardreas Olsson
told Yahoo News. "I'm not sure what you will see when you go down. But I'm excited. It's going to be interesting to see what it is."
PHOTOS: ARE THESE UFOS?
Sunken Ship in the Baltic Sea