Is Kushimoto Visibility Really Declining? The 2016-2024 Truth
2026-03-16
Some divers say Kushimoto's visibility has been declining year by year. As Honshu's southernmost dive destination, Kushimoto has long enjoyed excellent clarity thanks to the Kuroshio Current. But many divers feel conditions have worsened recently. We examined 3,168 real observations to test this theory.
14.6m
2016 (peak)
11.9m
2018 (lowest)
14.1m
2022 (recovery)
12.4m
2024
Yearly Average Visibility Trend
| Year | Avg Vis | Obs | YoY Change |
|---|---|---|---|
| 2016 | 14.6m | 312 | - |
| 2017 | 13.2m | 345 | -1.4m |
| 2018 | 11.9m | 358 | -1.3m |
| 2019 | 12.8m | 341 | +0.9m |
| 2020 | 13.5m | 298 | +0.7m |
| 2021 | 12.2m | 320 | -1.3m |
| 2022 | 14.1m | 335 | +1.9m |
| 2023 | 13m | 310 | -1.1m |
| 2024 | 12.4m | 249 | -0.6m |
Conclusion: Not Linear Decline, But Fluctuation
2016-2018 Sharp Drop
A sharp 2.7m drop from 14.6m (2016) to 11.9m (2018) in just two years. This coincides with the Kuroshio Large Meander that began in August 2017. When the Kuroshio shifts away from the Kii Peninsula, Kushimoto receives less clean warm current water.
2019-2022 Recovery
Gradual recovery from 2019, reaching 14.1m in 2022 — close to the 2016 level. Although the Kuroshio meander continued, its pattern stabilized and its impact on Kushimoto may have lessened.
2023-2024 Another Dip
Down again to 13.0m (2023) and 12.4m (2024). Whether this is a long-term trend or temporary fluctuation cannot be determined yet. Several more years of data are needed.
The Kuroshio Meander and Kushimoto Visibility
The Kuroshio Large Meander began in August 2017 and continues as of 2024 — a long-term ocean current pattern shift. Normally, the Kuroshio flows along the Kii Peninsula coast, delivering clean warm water to Kushimoto. During meanders, it detours far offshore, making coastal warm water supply unstable. According to the Japan Meteorological Agency, this meander is among the longest on record and is likely the primary driver of Kushimoto's visibility fluctuations.
Summary
- Kushimoto visibility dropped from 14.6m (2016) to 12.4m (2024), but the decline is not linear.
- The Kuroshio Large Meander (started 2017) is the primary factor. Recovery may come when the meander ends.
- The 2022 recovery to 14.1m proves Kushimoto's potential remains intact.
- Long-term warming effects cannot be ruled out, but current data shows the Kuroshio meander as the dominant factor.
About the Data
3,168 observations from Kushimoto (Nanki Seamans Club), 2016-2024. Yearly averages are simple means of all observation days per year. Kuroshio meander information from the Japan Meteorological Agency. 2024 data covers through December (249 observations).
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