Yonaguni vs Ishigaki: Visibility, Temperature & Season Compared with Real Data
2026-03-11
Key Takeaways
- Yonaguni wins on raw visibility (+4m avg: 24.5m vs 20.5m) but is highly unpredictable day-to-day (AI R²=0.046)
- Ishigaki is remarkably stable (only 2.8m seasonal range) with Japan's best manta encounter rate
- For peak clarity: Yonaguni Sep-Oct. For reliable fun: Ishigaki year-round. Smart move: base at Ishigaki, day-trip to Yonaguni
Two Different Worlds Under the Sea
Yonaguni and Ishigaki are both in Japan's remote southwestern island chain, but they offer fundamentally different dive experiences. Yonaguni is Japan's westernmost island (127 km from Taiwan), battered by the Kuroshio Current — raw, unpredictable, legendarily clear. Ishigaki, the gateway to the Yaeyama Islands, offers stable coral reefs, near-guaranteed manta encounters, and beginner-friendly conditions.
We compared both using 6,000+ real dive observations.
Key Statistics
| Metric | Yonaguni | Ishigaki | Notes |
|---|---|---|---|
| Avg visibility | 24.5m | 20.5m | Diff: +4.0m (Yonaguni) |
| Max recorded | 50m | 40m | Yonaguni's 50m is legendary |
| Min recorded | 0m | 5m | Yonaguni crashes after typhoons |
| Seasonal range | 4.9m | 2.8m | Ishigaki more stable |
| AI accuracy (R²) | 0.046 | 0.306 | Yonaguni nearly unpredictable |
| Total observations | 4,826件 | 1,473件 | Yonaguni has more data |
| Avg water temp | 26.2°C | 24.9°C | Yonaguni slightly warmer |
Monthly Visibility: Seasonal Patterns
| Month | Yonaguni (m) | Ishigaki (m) | Difference |
|---|---|---|---|
| Jan | 22.4 | 20.9 | +1.5m |
| Feb | 22.6 | — | — |
| Mar | 23.5 | 21.9 | +1.6m |
| Apr | 23.9 | 21.2 | +2.7m |
| May | 24.2 | 20.1 | +4.1m |
| Jun | 24.4 | 20.1 | +4.3m |
| Jul | 25.6 | 20.9 | +4.7m |
| Aug | 26.5 | 21.0 | +5.5m |
| Sep | 27.3 | 21.4 | +5.9m |
| Oct | 26.8 | 19.4 | +7.4m |
| Nov | 24.4 | 19.1 | +5.3m |
| Dec | 23.4 | 19.4 | +4.0m |
Visibility: Yonaguni Wins by +4m
Yonaguni averages 24.5m vs Ishigaki's 20.5m — a consistent +4m advantage throughout the year. The peak difference is September (27.3m vs 21.4m = +5.9m). Yonaguni's clarity comes from its direct exposure to the Kuroshio Current: no large adjacent landmass, virtually no terrestrial nutrient or sediment input, and constant circulation of oligotrophic oceanic water.
Stability: Ishigaki Wins
Ishigaki's seasonal range is just 2.8m (19.1m–21.9m) — remarkably consistent. Yonaguni swings 4.9m (22.4m–27.3m) and can crash dramatically: its minimum recorded visibility is 0m, versus Ishigaki's floor of 5m.
Yonaguni's visibility can suddenly drop to 10–15m even on calm, sunny days. The cause: Kuroshio path shifts form cold eddies around the island without warning. Environmental data (weather, waves) can't capture this — hence the near-zero AI prediction accuracy. Always check with local dive operators before committing to the trip.
Dive Character: 180° Different Experiences
Yonaguni
- Terrain: Vertical walls, the Yonaguni Monument (mysterious rock formation), hammerhead shark stations
- Signature wildlife: Scalloped hammerhead schools (winter/spring), giant trevally, dogtooth tuna
- Best for: Advanced divers, pelagic/drift diving, open-ocean adventures
- Best season: September–October (peak clarity), January–April (hammerheads)
Ishigaki
- Terrain: Coral reefs (Shiraho, Japan's largest Acropora reef), sandy bays, manta stations
- Signature wildlife: Manta rays year-round (especially June–September), sea turtles, macro life
- Best for: All levels, underwater photography, family trips
- Best season: May–October (manta guaranteed), but good year-round
Which Should You Choose?
| Goal | Pick | Reason |
|---|---|---|
| Maximum visibility experience | Yonaguni | Avg 24.5m, 27m+ in September |
| Guaranteed good conditions | Ishigaki | 2.8m variation, 19–22m year-round |
| See manta rays | Ishigaki | Manta Scramble — Japan's best |
| See hammerhead sharks | Yonaguni | Largest hammerhead school in Japan |
| Beginner / family trip | Ishigaki | Mild currents, diverse sites |
| Advanced / adventure diver | Yonaguni | Strong currents, open-ocean drift |
Summary
- Yonaguni wins on raw visibility (+4m): avg 24.5m, peaking at 27m in September
- Ishigaki wins on stability and predictability: 2.8m variation, AI R²=0.31
- Best for Yonaguni: September–October (clarity peak) + January–April (hammerheads)
- Best for Ishigaki: May–October (manta season), but reliable year-round
- Smart move: base yourself at Ishigaki and fly day trips to Yonaguni (30-minute flight)
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