Yonaguni sits at the western edge of Japan's Ryukyu chain, exposed to the open Pacific and shaped by the Kuroshio Current. All diving here is by boat, and drift diving is the standard format across the three sites in our database: the Yonaguni Monument, Hammerhead Rock, and Nakanougan-jima. Visibility is consistently high, ranging from the mid-twenties to sixty metres at the Monument and thirty to fifty metres at Hammerhead Rock, though strong and unpredictable currents make conditions demanding. The water stays warm year-round, cooling to the low-to-mid twenties in winter and climbing to thirty degrees in summer. Sites suit advanced and intermediate divers; beginners are not catered for here.
Monthly water temperature across Yonaguni's sites, from satellite sea-surface data corrected for depth. The band shows the site-to-site spread.
Winter brings the coolest water, settling into the low-to-mid twenties, but visibility peaks and conditions can be exceptional for drift diving. Summer temperatures reach thirty degrees but currents remain strong throughout the year, so thermal comfort never fully replaces the need for experience and current awareness.
Water temperature around Yonaguni ranges from about 24°C in January to 29°C in July, based on satellite sea-temperature data for its dive sites.
In the warm season (about 29°C) a rash guard or 3mm shorty is comfortable in Yonaguni; in the coldest months (about 24°C) step up to a 3mm full suit.
Fin maps 3 sites in Yonaguni (3 scuba diving sites).
