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.

Committing cold-season diving off Japan's westernmost island. You hook onto the reef in ripping current and hang there while schools of hammerhead sharks pass in the blue — a gathering that happens in numbers almost nowhere else.

The current is strong enough to be the defining feature, and winter seas frequently cancel whole days at a stretch, so patience is part of the deal.

The same island holds Yonaguni's submerged rock terraces — a sunken monument to some, natural geology to others — which you can dive over and judge for yourself. Water sits around a bracing twenty-two degrees through the hammerhead season.

Book with a Yonaguni operator for the hammerhead season, roughly December to March, and expect some days to be blown out by winter weather, so allow spare time in your trip. Operators require advanced certification and logged experience because the current is very strong; drift-diving and reef-hook skills matter here.

Reach the island by short flight or ferry from the main Okinawan islands. Bring a warm enough wetsuit for twenty-two-degree water and long hangs in current. If sharks are the goal, prioritise the peak weeks — and ask to dive the underwater 'monument' on a calmer day.