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Overview
Open-water drift along the Kuroshio current off Cape Irizaki, the westernmost point of Japan, where scalloped hammerheads gather through winter — schools of 100 to 200 sharks are logged from January to March. There is no reef to hide behind: divers make a negative entry, drop fast and hover near 15–20 m in open blue water over a seabed close to 70 m, watching the current line for the massed sharks. Dive operator Kihachiro Aratake was scouting this hammerhead ground in 1986 when he came across the nearby Yonaguni Monument. Between shark passes the same current draws in dogtooth tuna, great barracuda and bigeye trevally, with the odd sailfish. Visibility often runs past 30 m, but winter north winds cut it back and regularly cancel boats.
Briefing note
Demanding blue-water drift — most operators require Advanced Open Water plus solid deep and current experience, and many ask for 50–100+ logged dives. Expect a negative entry, fast descent and short bottom times on a current that can run hard and change direction; there is no bottom within reach, so reef hooks are not used. The Kuroshio and strong northeast winter winds frequently cancel boats from December through February, and hammerhead sightings are never guaranteed. Yonaguni has no recompression chamber — the nearest is on Okinawa's main island and evacuation is air-only.
What you'll see
5 species curated- seasonalScalloped hammerhead sharkPeak: Jan · Feb · Mar
- year-roundDogtooth tuna
- year-roundGreat barracuda
- year-roundBigeye trevally
- rareIndo-Pacific sailfishPeak: Jan · Feb · Mar
Conditions
| Month | Water | Visibility | Current |
|---|---|---|---|
| Jan | 21–23 °C | 20–40 m | strong |
| Feb | 21–23 °C | 20–40 m | strong |
| Mar | 22–24 °C | 20–40 m | strong |
| Apr | 23–25 °C | 20–35 m | moderate |
| May | 24–26 °C | 15–30 m | moderate |
| Jun | 26–28 °C | 15–25 m | moderate |
| Jul | 27–29 °C | 15–25 m | moderate |
| Aug | 28–29 °C | 15–25 m | moderate |
| Sep | 27–29 °C | 15–25 m | strong |
| Oct | 25–27 °C | 15–30 m | moderate |
| Nov | 23–25 °C | 20–35 m | strong |
| Dec | 22–24 °C | 20–40 m | strong |
Season calendar
Peak season highlighted · current month outlined
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