Slackwater vs AyeTides

Both apps compute bundled tide and current predictions on the phone without signal. Slackwater's Canadian stations need an initial download, and some passes remain online-only. AyeTides has done it since 2008 for $7.99 once, covers 13,400 locations worldwide, and has a Watch app. Slackwater is free, shows you the slack window rather than a table and covers Canadian passes from CHS data.

If you already own AyeTides and it answers your questions, there is no reason to leave it.

Slackwater features checked October 9, 2026. AyeTides' price, rating and features checked against its US App Store listing on October 14, 2026. AyeTides XL is the iPad edition and does not run on iPhone.

At a glance

Side by side

AyeTides	Slackwater
AyeTides' own App Store screenshot: a day at Bergen Point as a list of events with the graph underneath.	Slackwater at St Martins in the Bay of Fundy: the state and height first, its rate of rise, the curve you scrub, and the range.

AyeTides' listing shows no current station screen, so there is nothing to put beside this one. Here is Slackwater's:

Nakwakto Rapids at 5:40am, approaching slack at 0.5 kn, with the 10.3 kn ebb before it and the 5.2 kn flood after. The green runs on the line are the slack windows.

Currents

AyeTides gives you the real thing: harmonic current stations with predicted slack and max times in a table. That is more than most tide apps manage.

Slackwater starts from the same kind of data and answers a different question with it. The detail view leads with the state now, the next slack and how long it lasts, then max flood and max ebb with speed and set, over a curve you drag through the week. The reference port's tide is on the same screen. Current cards in the list turn green for each usable slack window. You read the window, not the table.

Canada

This is where the two part. AyeTides' BC current coverage is thin, and paddlers have reported stations placed on land. That is measurable from AyeTides' own public station list, measured October 14, 2026: 364 of its 442 BC stations are positioned to the nearest arc-minute, and where one of those shares a name with a CHS station it sits a median 700 m from CHS's position, against about 130 m for the stations with full-precision coordinates. Slackwater's Canadian gates come from Canadian Hydrographic Service predictions, fitted on the device and checked against CHS's published numbers before they ship. The list today is 23 gates from Active Pass and Seymour Narrows out to Cape Breton. A few sit in water the on-device model cannot fit, so those fetch when you have a signal and say so.

Canadian tide ports need an initial download of CHS predictions to build their offline model. Check that the download is complete before leaving signal.

Coverage everywhere else

Both apps predict tides worldwide. Slackwater ships thousands of tide stations, each one naming its source, datum and licence, from an open dataset that is maintained. AyeTides lists 13,400 locations, tides and/or currents, and does not say per station where the constituents came from or when they were last updated. Two in three of its stations outside the US appear to date from harmonic tables published before 2001, and cannot be refreshed from any live source.

Where AyeTides genuinely has more is current stations outside the US and Canada. Slackwater's currents stop at the border on purpose: that is where it can check every station against the agencies' own predictions before it ships.

Interface

AyeTides leads with the day's events as a list, with a graph you drag below it or full screen when you rotate the phone. It was updated for Liquid Glass in January. Slackwater is built for iOS 26, with the curve on every card, a scrubber that follows your thumb, and a chart that draws offline. Whether that is worth anything to you depends on how you read a table.

Price and trust

$7.99 once, with no ads, in-app purchases or subscriptions, is the most trustworthy pricing in the category and AyeTides earned its reputation on it. Slackwater's tide charts, current predictions and home screen widgets are free, without a subscription. Optional Premium adds alerts, station calendars, lock-screen widgets and Watch complications, with annual and lifetime purchase options. The engine, the app and the station data are open source, so the numbers can be checked by anyone.

Who should pick which

AyeTides if you need current stations outside the US and Canada, use iNavX, want notifications and calendar events without a subscription, or want a finished product with years of updates behind it.

Slackwater if you transit passes in BC or the Pacific Northwest, want the slack window and its duration without reading a table, or want free and open.

Nothing imports between them. Star your stations in Slackwater by search; they sort nearest first.

Predictions are not observations. Weather, river flow and local conditions change the water. Neither app is for navigation.

Download Slackwater on the App Store · Free, no account. Requires iOS 26 or later.

See also: the best tide and current apps for iPhone · Slackwater vs Actual Currents · Slackwater vs Dairiki.org