Worth
it?
Sendoa checks the sea for you. Tide, swell, wind, light. One verdict per spot, a window, the reasons. Nothing else.
Sendoa
Sendoa is a Basque name. It comes from sendo: solid. That is the word for a swell that holds — long enough, clean enough, serious enough to be worth the drive. Whether it holds today, and at what time, is about the only thing anyone asks of a forecast. The app is built around that question and around the curve that answers it: the day's tide, under a sky that follows the spot's real solar time, with swell, wind and light laid over it.
One glance, one answer
Every spot says whether it's worth it today, at what time, and why. In a sentence, not a table.
Tides that are yours forever
Our own harmonic constants for France, fitted to SHOM's open observations; NOAA's and TICON-4's elsewhere. On your phone. No network, no subscription, no drift.
Honest data
Sources named, freshness shown, uncertainty said out loud beyond three days. Never fake precision.
Made for the beach
Black, high-contrast, one hand, wet fingers. Lock-screen widgets: next tide and coefficient.
Tides you can check.
57 harmonic constituents fitted to two and a half years of hourly observations per port, then verified on seven held-out months. At Brest the median error on our high waters is under a minute against SHOM's observations, and the coefficient matches to the point. Outside France, times are checked against a month of tide-gauge readings: thirteen Spanish ports out of thirteen land within four minutes of mean error, and nine British ports out of nine within eight.
RECEIPT · ACCURACY · JUL 2025 → JAN 2026
| PORT | MEDIAN | MEAN | HEIGHT |
| Brest | 0,1 min | 4,0 min | 14 cm |
| Saint-Malo | 1,4 min | 5,2 min | 18 cm |
| Roscoff | 0,1 min | 4,2 min | 17 cm |
| Les Sables-d'Olonne | 0,1 min | 7,2 min | 15 cm |
| Bayonne – Boucau | 0,0 min | 4,4 min | 11 cm |
| Saint-Jean-de-Luz – Socoa | 1,4 min | 5,2 min | 9 cm |
| HW/LW vs real observations (weather included). Source Shom/REFMAR, open licence. Computed by Sendoa. | |||
Dunkerque · Calais · Boulogne · Dieppe · Le Havre · Cherbourg · Saint-Malo · Roscoff · Brest · Audierne · Concarneau · Port-Tudy · Saint-Nazaire · Les Sables · La Rochelle · Port-Bloc · Bayonne · Saint-Jean-de-Luz · Sète · Marseille · Toulon · Nice · Ajaccio · Bilbao · Santander · Gijón · A Coruña · Vigo · Cádiz · Las Palmas · Newlyn · Ilfracombe · Milford Haven · Holyhead · La Jolla · Santa Monica · San Francisco · Honolulu · Montauk · Sydney · Newcastle · Coffs Harbour · Lorne · Fremantle · Cape Town · Simon's Town · Port Elizabeth · Durban …
The full reportSecret spots.
A spot you'd rather not share? Drop a pin on the map, say which way the beach faces and which tide you like: Sendoa computes tide, swell, wind and verdict like for any other spot. It stays on your phone. We compute, we show it to no one — the forecast request leaves your phone only as a 1 km cell.
One price. Once.
€4.99, no subscription, no ads, no account, no trackers. You buy the app, it's yours, and it still works in ten years on a beach with no signal. Family Sharing included.
€4.99 · iPhone · iOS 26+ · in English, French and Spanish · Secret spots option at €4.99, once as well
Where do swell and wind come from?
From Open-Meteo, which assembles Météo-France models (AROME, ARPEGE, MFWAM) and ECMWF/Copernicus. We route them through a small cache so the app stays fast and the subscription is on us, not you.
Which countries?
France, Spain, the United Kingdom, the United States, Australia and South Africa: 227 spots and 340 tide ports. Every spot runs on its own beach's clock, in metres or feet, in km/h, mph or knots. The app speaks English, French and Spanish. Your spot isn't there? Ask for it from the app.
Whose tides are these?
Our own computations. In France, from SHOM's open observations (REFMAR, open licence); in the United States, from the constants NOAA publishes; elsewhere, from TICON-4 (DGFI-TUM, CC-BY 4.0). They are no hydrographic office's official prediction, but we publish our accuracy port by port. For navigation, use official documents.
Does it work offline?
Tides, yes, always. Swell and wind show the last forecast received, with its time.
Do you track my location?
No. Sendoa never asks for location: you pick your spots. No usage statistics, no trackers — nothing leaves your phone except the forecast request.
My spot isn't there.
In the app, "My spot isn't there" sends us your spot (name, landmarks, pin) and your e-mail so we can reply. Every spot is reviewed with people who surf it before it's added. And if you'd rather keep it to yourself: the Secret spots option.
What is the Secret spots option?
A one-time €4.99 purchase that lets you add your own spots, unlimited, with the same verdict as the others. They are never shown to anyone and stay on your phone.