# Slackwater

Slackwater is a free, open-source tide and tidal currents app from [Open Waters](https://openwaters.io/), published by Open Water Software LLC. It runs on iPhone and iPad with iOS or iPadOS 26 or later, and on Apple Watch with watchOS 26 or later.

[Download on the App Store](https://apps.apple.com/app/slackwater-tides-current/id6813654837).

An Android version is in development. Join the [Slackwater Android testers group](https://groups.google.com/g/slackwater-android-testers) with the Google account you use on your phone to get test builds through Google Play as they become available.

## Tides and currents

Check high and low tides, current speed and direction, and slack-water times for a beach visit, fishing trip or passage. Scrub the timeline to see conditions at a chosen minute, with a week of highs, lows, maximum currents and slacks below. The app shows sunrise, sunset and moon phase alongside the predictions. Search for stations, browse the map, or use location permission to find nearby stations. Location permission is optional and your GPS coordinates stay on your device.

Tide stations are available around the world; current stations cover the US and Canada. Coverage varies by place. [Browse the station directory](https://slackwater.xyz/stations/) to check your destination. Website coverage is not identical to the app's coverage.

## Widgets and Apple Watch

Free home screen widgets show the next high, low or slack and today's curve, for your location or a station you choose. To add one, long-press your home screen, tap +, and search for Slackwater. The free Apple Watch app works without your phone; turn the Digital Crown to move through the day. Premium adds lock-screen widgets and Watch complications.

## Offline use

Bundled stations predict on your phone for any date without a download or an expiring cache. Supported Canadian stations need an initial download to build an offline model. Some Canadian passes require a connection and are labeled in the app. Set up Canadian stations before leaving signal. Canadian station pages on this website fetch predictions directly from the Canadian Hydrographic Service in the browser; raw HTML and Markdown do not contain those predictions.

## Free features and Premium

Tide charts, current predictions, station search, favorites, home screen widgets and the Apple Watch app are free. Choose any prediction date without a subscription. There is no Open Waters account and no ads. Favorites can sync through Apple's iCloud.

Optional Premium adds alerts, station calendars, lock-screen widgets and Watch complications, with annual and lifetime purchase options. See [pricing and purchase terms](https://slackwater.xyz/pricing/) for US prices, subscription renewal terms and local pricing information.

## Prediction sources and limits

NOAA predictions use published harmonic constituents. Most Canadian stations build a model on your phone from Canadian Hydrographic Service predictions after a download; some passes fetch predictions online. The engine is checked against agency predictions. The [accuracy report](https://slackwater.xyz/accuracy/) gives dates, methods and limits for the published validation samples.

Predictions are not observations. Weather and river flow affect conditions. Slackwater is not for navigation.

## More information

- [About Slackwater](https://slackwater.xyz/about/)
- [Contact](https://slackwater.xyz/contact/)
- [Support](https://slackwater.xyz/support/)
- [Privacy](https://slackwater.xyz/privacy/)
- [How tides work](https://slackwater.xyz/learn/tides/)
- [What is slack water?](https://slackwater.xyz/learn/slack-water/)
- [OpenCPN database](https://slackwater.xyz/opencpn/)
- [App source code](https://github.com/openwatersio/slackwater-ios)