The Yonaguni Monument, also called Yonaguni Island Submarine Ruins, is an underwater rock formation south of the Japanese Ryukyu Islands, about 100 km east of Taiwan. Some scientists claim that the rock structures are stepped monoliths made by humans, and have existed for more than 10,000 years. It certainly looks more man-made rather than natural, but no official research or preservation efforts have been conducted on the site.
Discovered in 1986 by a diver, the site has also attracted scientists' attention. Masaaki Kimura, a marine geologist at the University of the Ryukyus, has been studying the object for many years and is convinced that the site was carved thousands of years ago when it was still above water. Precise angles and triangle carvings are unlikely to have a natural origin. He believes that the structure could be the remains of the Lost Continent of Mu, the Japanese Atlantis. However, other scientists don't agree and insist that geology and strong currents are responsible for the unusual shape of the rock.
Yonaguni Jima is an island near the southern tip of Japan's Ryukyu archipelago. Experienced divers can enjoy drift diving off the island year round. Even though the Monument is located close to the shore and it’s a shallow dive between 4.5 to 12 m (15 to 40 feet), sometimes the area is subject to strong currents, so divers have to be careful. From November to June you can spot schools of hammerhead sharks in the area.