The Baltic anomaly

In 2011, between Sweden and Finland, at the bottom of the Baltic Sea, at a depth of 87 meters, Swedish scientists discovered an unknown large-sized object with a regular round shape of 18 meters. On the surface of the object there are protrusions and depressions of the correct shape. The object was named the Baltic anomaly. Someone thinks that this is a UFO, someone is a shelf formation as a result of the movements of an ancient glacier. Disputes led nowhere, research ceased and the object was gradually forgotten.