Scientists have identified who dug the strange depressions at the bottom of the North Sea

German researchers have always been sceptical about the theory that pits formed due to methane leakage. During the expedition, they indeed found no evidence of shallow gas.

Then the experts armed themselves with a multibeam echo sounder to get a good look at the pits. As it turned out, they did not have a cone shape, as if a jet of methane gas had broken through the sediments. But all the pits had the same depth – about 11cm.

To understand the reason for this, one of the scientists phoned an acquaintance, a biologist and diver, who told him that porpoises were scurrying around the seabed trying to find sand eels.