Kimura Masaaki is a Japanese marine geologist and professor emeritus at the University of the Ryukyus.
Since the 1990s he has conducted diving surveys of the Yonaguni Monument in Okinawa Prefecture, arguing that its step-like terraces and right-angled walls show signs of human working and that it is an ancient site, once on land, that sank into the sea. Other geologists counter that it is a natural formation, and the debate continues.
