Back in 2011, sonar picked up a massive, perfectly circular object 90 meters beneath the Baltic Sea, complete with straight edges and a strange drag mark trailing behind it. The Swedish exploration team behind the find had no history with UFOs, but headlines instantly screamed alien spacecraft.
In June 2011, a Swedish exploration team called Ocean X was scanning the floor of the northern Baltic Sea with side-scan sonar, searching for shipwrecks. The team, led by Peter Lindberg and Dennis Asberg, had been at sea for nine days and was preparing to head home when they decided to run the sonar one last time. That final pass picked up an unusual shape on the seafloor at a depth of roughly 90…