Koganezaki Visibility Analysis — 1,100 Days of West Izu Macro Diving Data
2026-03-16
Koganezaki is West Izu's premier macro diving destination, famous for rare creatures like ornate ghost pipefish and seahorses. But its visibility also ranks among Izu's best. We analyzed 1,110 real observations to reveal Koganezaki's visibility patterns.
Key Stats
13.5m
Annual avg
1,110
Observations
15.8m
Peak (Mar)
9.7m
Low (Jul)
Monthly Visibility
Jan
16.2
Feb
15.7
Mar
15.8
Apr
12.8
May
10.7
Jun
13.2
Jul
9.7
Aug
14.7
Sep
11.6
Oct
15.4
Nov
12
Dec
14.2
Three Key Characteristics
1. Only Izu Site Where March Is Best
While IOP and Futo peak in January, Koganezaki hits its annual best of 15.8m in March. IOP is already at 13.7m and Futo 11.6m — spring bloom arriving. Koganezaki's West Izu geography delays the spring plankton bloom, keeping waters clear longer.
2. Unique Zigzag Seasonal Pattern
Monthly visibility zigzags dramatically: Mar 15.8m → May 10.7m → Jun 13.2m → Jul 9.7m → Aug 14.7m → Sep 11.6m → Oct 15.4m. Bi-monthly swings of 5m+. Likely caused by alternating Suruga Bay water mass exchanges.
3. Annual Average Nearly Matches IOP (13.8m)
Koganezaki's 13.5m annual average is just 0.3m below IOP (13.8m). Equivalent visibility but far less crowded. Travel time from Tokyo is similar (2.5–3hr drive). Choosing Koganezaki when IOP suffers spring bloom is a smart strategy.
Best Season Guide
Best: Jan–Mar
15.8–16.2m. Drysuit required but visibility is peak
Good: Aug & Oct
14.7m / 15.4m. Comfortable temps + good visibility
Caution: May, Jul, Sep
9.7–11.6m. Zigzag trough months
Macro Photography
Year-round. Macro works even in lower-visibility months
About the Data
1,110 real observations at Koganezaki (2006–Mar 2026). Visibility = mean of daily min/max. Source: dive shop daily reports.
🌊 Check Visibility Forecasts
View AI-powered 7-day visibility forecasts for 30+ dive sites across Japan.
Open Forecast App →