This app provides tide and current predictions that work offline, even without a signal. It offers detailed information on tide times, current speeds and directions, and celestial events for thousands of stations worldwide. Users can access this data on their iPhone, iPad, and Apple Watch.
1.15.0
November 11, 2026
Ask for an alert in your own words, plan around the golden and blue hour, and keep your place on iPhone Duo. · Type or dictate when you want an alert, such as "an hour before tomorrow's low" or "whenever it rises past 8 ft", and Slackwater fills in the alert for you to check. Apple's on-device model reads the sentence, so nothing leaves your phone. This needs an iPhone with Apple Intelligence. · Every tide and current timeline has a line for setting an alert. Press and hold the moment you care about, then tap the line. One sheet makes and edits every alert. · Alerts can be limited to daylight, the golden hour, or the blue hour, and can follow only the lower low or higher high of each day. Alerts are part of Slackwater Premium. · A Sun card sits beside the Moon with the next sunrise or sunset and the day's daylight. The Sun sheet lists golden hour and blue hour, and tapping any time in it moves the timeline there. · The Moon is drawn tilted the way it looks from the station. · Folding or unfolding an iPhone Duo keeps the moment, the week, and your place in the schedule. · Slackwater is available in Irish and Scottish Gaelic. · New Zealand tides use harmonic constants from Toitū Te Whenua Land Information New Zealand. · When a station's record changes, your favorites, alerts, widgets, and watch complications follow it. A station Slackwater no longer carries says so and suggests nearby replacements. · Canadian downloads carry on in the background when you reopen the app. On online current stations, the timeline moves on into the next week and downloads it. Downloads shows whether you're online, and each online current station has one control for its expiry and updates. · The timeline stops where your finger lifts, unless an event is within 15 minutes. · A Help link in Settings opens Slackwater's support page. · Current timelines tell slack from the slack window. The line is blue inside the slack window you set in Settings and yellow outside it, where the reading keeps saying Flooding or Ebbing. Only the zero instant is green and reads Slack; the comfort current defines the window, not slack. The timeline names the slack window opening, slack, and the window closing as three moments, and the comfort current in Settings steps down to Off for slack alone. Off reaches other devices once they run 1.15 too. · Fixes: tapping an alert notification no longer crashes Slackwater when it has been in the background; the widget, Siri, and the station card agree on the next tide at places where the tide is very small.
MoreYearly Premium. Support Slackwater.
No, Slackwater is ad-free. The app explicitly states it has no ads and no tracking, ensuring an uninterrupted user experience.
Slackwater uses data from official sources like NOAA and the Canadian Hydrographic Service, with predictions checked against published tidal datums where available. However, it notes that predictions are not observations and conditions can vary with weather and river flow.
Yes, Slackwater is designed to work offline. All tide and current predictions are made on your phone, meaning you get answers even without a signal.
Slackwater is available on iPhone, iPad, and Apple Watch. It also offers home screen widgets for quick access to information.
The core features of Slackwater are free to use. An optional 'Slackwater Premium' subscription is available for $7.99 per year, offering additional features like lock screen widgets and alerts.
The latest version is 1.15.0, last updated on November 11, 2026. While specific update frequency isn't detailed, the app receives regular updates to maintain functionality and data accuracy.
Slackwater also provides detailed current information, including slack, max flood, and max ebb speeds and directions. It also includes sunrise, sunset, twilight times, moon phases, and explanations of spring and neap tides.
No, Slackwater explicitly states that its predictions are not for navigation. While it provides detailed data, users should rely on official navigation charts and equipment.
