Okinawa, Japan
Yonaguni
Japan's westernmost island, 111km from Taiwan, sitting in the Kuroshio current, with a winter hammerhead aggregation and a large stepped rock formation whose origin is disputed.
- Scalloped hammerhead
- Hammerhead shark (unresolved species)
- Sharks
- Strong current
Best season
Best Jan–Mar
Minimum cert
Advanced + experience
Water
23–28°C
Current
strong
Season
When this place works
No formal closure, but two separate limiting periods. Jan-Mar is the hammerhead window and also winter: north-east monsoon wind cancels a high proportion of days, so you can book a week and dive twice. Jul-Sep is typhoon season in the…
Why dive here
What this place is known for
- 01sharkLow confidence
Winter hammerhead aggregation
Ranked first on its own merits, not as a consolation to the monument. Scalloped hammerheads school off Irizaki January to March. The trade is brutal and explicit: the schooling season is also the coldest water of the year (around 23C) and the strongest…
Seasonality — peakpeakpeakoffoffoffoffoffoffoffoffshoulder
02formationLow confidenceYonaguni Monument (Kaitei Iseki)
CONTESTED ORIGIN, and the dataset does not take a side. A stepped rock mass roughly 290m by 120m and 26m high, top terrace at about 5m and base at about 25m, 100m off Arakawabana Cape. Masaaki Kimura (Ryukyus) argues for human construction, citing…
03driftLow confidenceKuroshio current diving
The current is the reason both of the above exist: it delivers the hammerheads and it carved or exposed the monument. It is also why the island is a difficult destination rather than a popular one.
Marine life
Twelve-month species timelines
Jan-Mar schooling off Irizaki. Single source for the window; no research literature located. Unbaited.
Sources refer only to 'hammerheads' without consistently resolving species. Retained as a separate genus-level entry rather than assuming every reported animal is S. lewini. Merge these two entries…
Conditions
What the water is like
Water temp
23–28°C
15°C — 32°C
Visibility
15–30 m
0 m — 40 m
Current
strong
mild — strong
Thermoclines
Not typical
unlikely
Minimum certification — Advanced + experience
Low confidenceOne of the two or three most demanding destinations in this dataset. The Kuroshio runs hard and sources recommend Advanced plus roughly 100 logged dives. The hammerhead season is winter: coldest water, strongest current, roughest surface…
Entries — boat
Logistics
How people dive it
3-7 days
scuba
Small local operators; boats leave Irizaki harbour, nicknamed Shark Dock, and reach the monument in about 20 minutes. Getting to Yonaguni…
Operators
Who to book with
Loading operators…
Sources & verification
Check the evidence.
Every destination is independently researched and major claims link back to their sources.
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