Frequently asked questions
Everything people ask us about Tides Pro, in one place. Type to filter.
What is the tidal coefficient?
A number from 0 to 120 summarizing the day's tidal range. Below 40 we speak of neap tides (small range), 40–79 of average tides, and 80 upwards of spring tides: bigger range, stronger currents and usually better fishing and shellfishing. Full explanation in the coefficient guide.
How accurate are the tides?
The FES2022b harmonic engine is validated against reference ports of the Spanish Hydrographic Institute with a median error of about ±10 minutes on open coast. We'd rather give you the real margin than promise the impossible.
Why is the error larger inside rias and estuaries?
The tidal wave deforms as it travels through shallow water, narrow rias and river channels. A global model with ~12 km cells cannot fully capture that local propagation. The app tells you so, honestly, at the affected ports.
Does it work offline?
Yes. Tides, coefficient, fishing index and astronomy are computed on your device: they work with no coverage, on a boat or at the beach. Only the weather forecast needs a connection, as it comes from Apple Weather.
Why don't the times match my phone's clock?
Times are always shown in the local time of the selected port, not your device's. If you are in London checking the tides of Ponta Delgada (Azores), you'll see Azorean time. It's the most common source of confusion — and the right thing for planning on location.
Why are there negative heights?
Tides Pro expresses heights above mean sea level: a spring-tide low can dip below that level and show as negative (e.g. −1.1 m). Official tables use a different zero (the nautical chart datum), so absolute numbers differ between sources even though the range — the difference between high and low — matches. More detail in the tide-table guide.
How many ports are included? Can I add my beach?
90 ports across Spain (Cantabrian, Galicia, South, Strait and Canary Islands) and Portugal (mainland, Azores and Madeira), plus an international selection. And you can search any beach, cove or coordinate in the world: the app extracts the harmonic constants for the exact point you choose.
What does the app do on Apple Watch?
The watch app shows the tide right now (height, rising or falling, countdown to the next event), the day's curve and the coefficient, with watch-face complications that update by themselves as each tide passes. It syncs automatically from the iPhone.
Does the Live Activity drain the battery?
Very little. The Lock Screen countdown and progress bar are animated by the system itself without running the app, and data refreshes only at key moments. You can toggle it from the Maritime profile.
Are there ports outside Spain and Portugal?
Yes: an international reference selection — Brest, San Francisco, Cape Town, Sydney, Singapore and Tokyo — plus free search of any coordinate in the world.
Will there be an Android version?
Not planned. Tides Pro is a native iOS and Apple Watch app — Liquid Glass, Live Activity, WeatherKit, complications — and that is the focus. Being native is precisely what makes it fast and polished.
Is it free? Will there be a premium plan?
The app launches free with no ads. If a premium plan with advanced features arrives in the future, the essentials — today's tide, your port, the coefficient — will stay free. No surprises.