Diving in Yonaguni

Yonaguni is the last speck of Japan before Taiwan, a hundred-odd kilometres out from the main Okinawan islands, and in the cold months it does something almost nowhere else does: schools of hammerhead sharks gather in numbers off its coast. Divers hook onto the reef in ripping current and hang there, watching them pass in the blue.

This is committing diving. The current is strong enough that operators require advanced certification and logged experience, and winter seas frequently cancel whole days at a stretch. When it is on, though, there is nothing quite like a wall of hammerheads materialising out of the haze above you.

The same island holds Yonaguni's other mystery — the submerged rock terraces that some insist are a sunken monument and geologists insist are natural. You can dive over them and decide for yourself; either way you are floating above something strange. The hammerhead season runs roughly December to March, when the water sits around a bracing twenty-two degrees.

Strong current diving — operators require advanced certification and logged experience. Winter seas frequently cancel days entirely.