How the numbers are made, who runs it, and the limits
muutos Inc., Hiroshima, Japan. We also run the Miyajima tide site miyajimatides.com. We have no ownership ties to any dive shop, ferry company or booking platform.
Every morning at 06:00 JST this site pulls wave height, wave direction, wind speed and wind direction off Cape Maeda (the Blue Cave) from the Open-Meteo marine forecast and turns them into an open probability, using the thresholds local dive shops actually use: most of them close the cave at roughly 1.5 m of swell or in a strong northerly. Cape Maeda faces north, so northerly wind and swell are weighted more heavily.
○ (70% or more) usually means snorkel and dive tours run at the cave. △ (45–69%) is a shop-by-shop call on the day. × (under 45%) means the cave is most likely closed — tours usually still run, but move to an alternative site such as Sunabe (Ginowan) or Cape Zanpa.
Ferry status for Tokashiki, Zamami and Aka is a forecast for the Tomari–Kerama route: partial cancellations become likely from about 2.3 m of swell, and most sailings are cancelled above 3 m. Official cancellation notices come from the ferry operators.
Open-Meteo Marine / Forecast API (wave height, wave direction, wind speed, wind direction; 8–9 km grid). The official Cape Maeda flag status is also logged daily so we can score ourselves later.
This site shows a sea-condition tendency (a guide) — it is not a weather forecast service and not an operating notice from any shop or ferry company. Whether the cave is open is decided by each shop on the day and by the official Cape Maeda flag; ferries by the operators. We accept no liability for decisions made on this information.
Booking links are affiliate links (KKday, Klook, Viator, GetYourGuide, agoda). We may earn a commission when you book through them; the price you pay does not change.