Yonaguni is a small Southern Japanese island that has remarkable underwater features off its coast, at depths as little as 20 feet in places. They have led to continuous debate since their accidental discovery in 1995. The conventional wisdom is that the monolithic formations are natural in origin and composed of granitic sandstone. Dr. Robert Schoch, who twice visited and dived at the site, supports this view.
However, there is a persistent claim that the enormous edifices are in fact the remains of an ancient sunken city. This school of thought is led by Masaaki Kimura, a marine geologist from the University of the Ryukyus, who has been diving and studying at the site for over 15 years. Some have gone as far as to claim that the site as that of the lost city of Mu, a Pacific counterpart of Atlantis.
*Carl Feagans has published an extensive article debunking Masaaki’s claims(a) .