Shiodoki: Japan Tide Charts

Is today a good tide? Pick your port and see it 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 port you pick. See at a glance whether today is a spring or neap tide, and whether the water is rising or falling.

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.

Tides are calculated on your device from harmonic constants bundled with the app. It never 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 (¥1,000) — not a subscription, with no further charges.

Shiodoki covers 90 ports in Japan (Japanese ports only). It shows the ports closest to you with the distance to each (tides vary by location in both time and height). Free gives you one favorite port with the full feature set plus 3 days ahead in the weekly view.

WHAT YOU GET

• Pick a port and instantly see today's tide curve and high/low times
• Tide name (spring to young), moon age, sunrise/sunset, dawn/dusk windows
• Fully offline calculation (no network calls except the purchase flow)
• Nearby ports shown with distance, search by port or prefecture, favorites
• Text size Standard / Large / Extra Large, light and dark themes

SHIODOKI PRO (one-time ¥1,000)

• Multiple favorite ports / unlimited weekly look-ahead / notifications / widget No subscription. Restore Purchases anytime in Settings.

DATA SOURCES Tide calculations use data created by processing the tidal harmonic constants published by the Japan Meteorological Agency and the Japan Coast Guard, Hydrographic and Oceanographic Department. The app is not provided or endorsed by either agency.

DISCLAIMERS

• Tide heights shown are astronomical values calculated from harmonic constants, not measurements (heights are above each port's datum).
• This app is not for navigation. For navigation, use the tide tables published by the Japan Coast Guard.
• Actual tides can differ significantly due to weather such as air pressure, wind, and storm surge. Please check the weather and sea conditions yourself before heading out.