Shiodoki: Japan Tide Charts
Tide curve for 90 Japan ports
Only for iPhone
Free · In‑App Purchases · Designed for iPhone. Not verified for macOS.
iPhone
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 — not a subscription, with no further charges (see the App Store listing for current pricing).
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.
ON THE TIDE SCREEN
- 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 purchase)
- Multiple favorite ports / unlimited weekly look-ahead / notifications / widget
No subscription. Restore Purchases anytime in Settings.
WHERE THE TIDE DATA COMES FROM
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.
BEFORE YOU HEAD OUT
- 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.
Ratings & Reviews
- This app hasn’t received enough ratings or reviews to display an overview.
Refreshed the look of the Settings screen. No new features or changes to functionality.
The developer, Yuya Tanaka, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Collected
The developer does not collect any data from this app.
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
- Seller
- Yuya Tanaka
- Size
- 4.3 MB
- Category
- Weather
- Compatibility
Requires iOS 17.0 or later.
- iPhone
Requires iOS 17.0 or later. - Mac
Requires macOS 14.0 or later and a Mac with Apple M1 chip or later.
- iPhone
- Languages
- English and Japanese
- Age Rating
4+
- 4+
- In-App Purchases
Yes
- Pro – All Ports (Lifetime) $5.99
- Copyright
- © 2026 Yuya Tanaka