PRESENTING THE MYSTERY. Brainstorming!

According to the National Oceanic and Atmospheric Administration less than five percent of the world's oceans have been explored, meaning that 95% of what lies deep underwater on Earth has yet to be seen by human eyes.
Yoji Ookata, a freelance underwater photographer, while diving in the semi-tropical region of
Amami Oshima (Japan), roughly 80 ft below sea level, discovered something he had never seen. And as it turned out, no one else had seen it before either.
 |
| Scan this QR code to see the localization on your mobile dispositive. |
This is what Yoji saw:
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 center.
The mystery circle appeared to be the work of an underwater artist, carefully working with tools.
A drafting compass? Ruler? Set squares?
What do you think?