Stefan Hogeborn, one of the divers in the expedition, said he was perplexed by the shape and structure of the circular object, which is about 60 metres in diameter and rises three to four metres from the seabed. That’s roughly the size of a jumbo jet.

Adding to the mystery, the object was also reported to have a 400-metre-long trail leading away from it, similar in appearance to skid marks. Another smaller disc-shaped object was found nearby, also with apparent drag lines about the same length.