Yonaguni Monument

The Yonaguni Monument (Japanese: 与那国島海底地形, Hepburn: Yonaguni-jima Kaitei Chikei^?, lit. "Yonaguni Island Submarine Topography"), also known as "Yonaguni (Island) Submarine Ruins" (与那国（島）海底遺跡, Yonaguni(-jima) Kaitei Iseki), is a submerged rock formation off the coast of Yonaguni, the southernmost of the Ryukyu Islands, in Japan.

Masaaki Kimura, Professor Emeritus from the Faculty of Science at the University of the Ryukyus claims that the formations are man-made stepped monoliths. His ideas are disputed and there is debate about whether the site is completely natural, a natural site that has been modified or a man-made artefact. Neither the Japanese Agency for Cultural Affairs, nor the government of Okinawa Prefecture recognise the features as important cultural artefacts and neither government agency has carried out research or preservation work on the site.

The sea off Yonaguni is a popular diving location during the winter months due to its large population of hammerhead sharks. In 1987, while looking for a good place to observe the sharks, Kihachiro Aratake, a director of the Yonaguni-Cho Tourism Association, noticed some singular seabed formations resembling architectonic structures. Shortly thereafter, a group of scientists directed by Masaaki Kimura of the University of the Ryūkyūs visited the formations.

The formation has since become a relatively popular attraction for divers despite strong currents. In 1997, Japanese industrialist Yasuo Watanabe sponsored an informal expedition including writers John Anthony West and Graham Hancock, photographer Santha Faiia, geologist Robert Schoch, a few sport divers and instructors and a film crew for Channel 4 and Discovery Channel. Another notable visitor was freediver Jacques Mayol, who wrote a book on his dives at Yonaguni.

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