Diver and photographer Yoji Ookata, discovered deep sea Mystery Circle’s off the coast of Japan. On the seabed a geometric, circular structure measuring roughly 6.5 ft in diameter had been precisely carved from sand. It consisted of multiple ridges, symmetrically jutting out from the centre. I may look like the work of human, but it’s nature.. Underwater cameras showed that the artist was a small puffer fish who, using only his flapping fin, tirelessly worked day and night to carve the circular ridges.