In June, 2011, two Swedish treasure hunters were searching in the Baltic Sea for old bottles of champagne from shipwrecks when their sonar recorded this mysterious object on the ocean floor. No one knows what it is. The disc-shaped object is huge: 197 feet in diameter -- as big as a 747 jumbo jet. Its shape indicates that it is not a natural formation and appears to be made of a hard substance, such as concrete or metal.
Its disc shape has, of course, led some to label it a crashed flying saucer, yet experts who have examined the image cannot identify it. The sonar image reveals that it fell to the ocean floor, leaving a 4,000-foot gouge in the seabed before coming to rest. About 400 feet away is another unidentified object that might be related to the disc. It is speculated that they are part of a shipwreck or part of a discarded Russian submarine base.
The explorers -- Ocean X Team -- returned to the site last month (May, 2012) and have sent divers to verify the discovery and to explore it further. New pictures and video are forthcoming, they say. Watch a video here. What do you think it is?