Tidal zone guide

30 July 2024

Dive deeper into the world of Les Marées.
Here is the list of tidal zones offered in our catalog for the 2025 edition.
Indeed, each tidal zone has its own times and heights.
Choose the right tidal zone because 1 tidal zone = 1 tide calendar.

Consult our 2025 tidal-zones-guide here

In this guide, we specify the list of reference ports used to draw your calendars, the geographical area covered and indications of time corrections on the zone.

The ocean will never have been so transparent for you!

Understanding Tidal Zones

But what does the notion of “tidal zone” mean?
Hydrographic organizations define these zones based on:
– geographical boundaries
– of a reference port
– a hydrographic zero, the same as that used on nautical charts.
– In general, the reference port of a zone is its main port.

On the French coast, SHOM offers 23 “main” ports from Dunkirk to Saint-Jean-de-Luz via Cherbourg, Brest or Saint-Nazaire.
SHOM calculates tides for hundreds of locations on the coastline, from “attached” ports to main ports. For greater accuracy, consult the official SHOM website.

A tidal zone = a tidal calendar.

Tidal zones on les-marees.com

With 33 different tide calendars covering the west coast of France, the Atlantic, the English Channel and the North Sea, we offer information for the main ports in the tidal zones and some “attached” ports within. a zone. View the calendars we offer on the coast map and consult our guide at the bottom of the page to find out the data used.

Make corrections to the tidal zone

To ensure optimal accuracy, corrections may need to be applied to tide times and heights across the entire geographic area of a major port.
Let’s take the example of the tidal zone of the port of SAINT-MALO, the zone of the largest tidal range on the French coasts. The tide predictions made for Saint-Malo can be used for the coastline going from the tip of Cotentin almost to St-Quay-Portrieux in the Côtes d’Amor according to SHOM.
Of course in this area from north to south it will be necessary to make corrections to the times and heights to refine the predictions depending on where we are.
In Cancale add +10 to +15 minutes for low water compared to Saint-Malo.
At Erquy remove – 10 to – 20 minutes at low water.
At St-Quay-portrieux remove – 5 minutes for high seas and – 15 to – 25 minutes for low water compared to Saint-Malo.

This is why we offer specific time corrections for the tide zone at the bottom of our tide calendar (non-exhaustive information). However, note that we do not mention water height correction. To refine these corrections, we recommend that you consult the official website of the National Hydrographic Service. SHOM.

Hours used

Our tide calendars are valid in legal times :

UT1 and UT 2 for France and Germany.
UTO and UT1 for England and Portugal.

When consulting a tidal calendar, always check its origin, the area concerned, the year and the legal or illegal times.

Do you know your data source for tide predictions?

The secret to an accurate and reliable tide calendar lies in the source of the data used. At les-marees.com we only use data provided by official organizations. In France, the Hydrographic and Oceanographic Service of the Navy (SHOM) forecasts tide times and heights for 23 “main ports”. Across the Channel, the UKHO (United Kingdom Hydrographic Office) is the reference body, as is the BSH (Bundesamt für Seeschifffahrt und Hydrographie) in Germany.

At the bottom of each of our tide calendars, we specify the provenance of the sources and our license to use the data.

In conclusion, with a good understanding of tidal zones and a reliable source of data, you can fully enjoy your coastal activities in complete safety.

Visualize the boundaries of the tidal zones : guide-zones-marees-2025

Zoom on a french curve