Is Japan's Diving Visibility Recovering in 2024–2025? A 10-Year Trend Analysis
2026-03-15
'The ocean seems clearer lately' — more divers have been saying this. Our data confirms: after bottoming out at 12.6m in 2021, the national average has recovered to 13.9m in 2024 and 14.1m in 2025. However, the recovery isn't uniform — some sites are rebounding while others remain stagnant.
Yearly Visibility Trend (National Average)
| Year | Avg Vis | Obs | YoY |
|---|---|---|---|
| 2016 | 14m | 1,853 | - |
| 2017 | 13.6m | 2,415 | -0.4m |
| 2018 | 13.3m | 3,163 | -0.3m |
| 2019 | 12.8m | 3,884 | -0.5m |
| 2020 | 13.1m | 3,684 | +0.3m |
| 2021 | 12.6m | 4,763 | -0.5m |
| 2022 | 12.8m | 5,046 | +0.2m |
| 2023 | 13.3m | 4,838 | +0.5m |
| 2024 | 13.9m | 4,456 | +0.6m |
| 2025 | 14.1m | 5,353 | +0.2m |
2021 Was the Bottom, 3 Consecutive Years of Improvement
After dropping 1.4m from 2016 (14.0m) to 2021 (12.6m), visibility has recovered to 2024 (13.9m). 2025's 14.1m is approaching 2016 levels.
By Site: Which Are Recovering and Which Aren't
| Site | 2021 | 2024 | Change |
|---|---|---|---|
| IOP | 12.8m | 13.9m | +1.1m |
| Futo | 11.4m | 12.5m | +1.1m |
| Kushimoto | 11.5m | 11m | -0.5m |
| Yonaguni | 23.1m | 24.2m | +1.1m |
| Echizen | 9.4m | 7.8m | -1.6m |
Recovering: IOP, Futo, Yonaguni
Pacific-facing open ocean sites recovered by +1m or more. Kuroshio path changes and shifts in the post-2017 Large Meander pattern may be contributing factors.
Stagnant/Declining: Kushimoto, Echizen
Kushimoto is flat to slightly worse (-0.5m). Echizen dropped -1.6m significantly. Sea of Japan sites are governed by different factors — Tsushima Current variability and coastal nutrient input.
What's Driving the Recovery?
Long-term visibility changes involve multiple interacting factors, making it difficult to isolate a single cause. Possible contributors include:
- Kuroshio Large Meander (2017–) pattern shifts. Meander position and intensity vary yearly, affecting Pacific-side sites.
- El Niño/La Niña effects. Post-2023–24 El Niño Pacific water temperature changes.
- Changes in data collection sites (statistical effects from adding new sites).
References: JMA El Niño monitoring reports, JAMSTEC Kuroshio meander monitoring
About the Data
Annual averages from 42 nationwide dive shop daily logs. Pre-2016 excluded due to small sample sizes. 2026 is provisional (through March). New site additions may affect the average through composition changes.
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