The researchers only realized afterwards that they had discovered something extraordinary. In September 2021, he actually just wanted to show his students how to use different measurement methods, says marine geologist Jacob Geersen. For a geophysical internship at the Christian Albrechts University in Kiel, he went to the Bay of Mecklenburg with a group of students and, among other things, mapped the subsurface there. “The seabed is usually more exciting than you imagine,” says Geersen. You can find traces of anchors or trawl nets there. But Geersen only understood that this time they had stumbled upon something very special when he later saw the footage on his screen.