Shiodoki: Japan Tide Charts

Today's tide and fishing windows — pick your spot and see them in about 3 seconds.

Shiodoki is a tide chart that instantly shows the tide curve, high/low times, tide name, moon age, and the dawn/dusk windows for the station you pick. Home opens with the next window (dawn/dusk and tide-change times), and sliding your finger along the tide line shows the height at that time and whether the water is rising or falling. The next 7 days are on Home too.

Everything an angler in Japan needs on one screen: the tide name (spring, middle, neap, long, young), moon age, sunrise/sunset, and the dawn/dusk windows. Choose text size Standard / Large / Extra Large, with light and dark themes.

Shiodoki covers 239 tide stations in Japan (Japan Meteorological Agency and Japan Coast Guard). It shows the stations closest to you with the distance and direction to each (tides vary by location in both time and height). Free gives you one favorite station with the full feature set plus 3 days ahead in the weekly view.

For 90 of the 239 stations, tides are calculated on your device from harmonic constants bundled with the app. For the other 149, the app shows the high/low waters and hourly heights of the JMA Tide Tables (predicted tides), bundled with the app (through December 31, 2027). Neither fetches weather data, so it works on remote shorelines, offshore, and on a boat with no signal. There are no network calls except the App Store purchase.

There are no ads at all — no full-screen ads, and no ad audio that plays through silent mode. The only purchase is the one-time Shiodoki Pro — not a subscription, with no further charges.

ON THE TIDE SCREEN
- The next window, the height now, and rising/falling at the top of Home
- Slide along the tide line to read the height at any time (it snaps to high and low water)
- Tide name (spring to young), moon age, sunrise/sunset, dawn/dusk windows
- The next 7 days, and a small tide line for each day of the week
- Nearby stations with distance and direction, search by name or prefecture, favorites
- Text size Standard / Large / Extra Large, light and dark themes

SHIODOKI PRO (one-time purchase)
- Multiple favorite stations / unlimited weekly look-ahead / notifications / widget
No subscription. Restore Purchases anytime in Settings.

WHERE THE TIDE DATA COMES FROM
- 90 stations: data created by processing the tidal harmonic constants published by the Japan Meteorological Agency and the Japan Coast Guard, Hydrographic and Oceanographic Department.
- 149 stations: based on the JMA "Tide Tables" (predicted tides). Highs/lows closer than 5 cm are merged for display, and heights between the hours are interpolated.
The app is not provided or endorsed by either agency.

BEFORE YOU HEAD OUT
- Tide heights shown are calculated or predicted astronomical values, not measurements (heights are above each station's datum).
- This app is not for navigation. For navigation, use the tide tables published by the Japan Coast Guard.
- Actual tides ca