This is the passage to the west of Brest, between the mainland and Ouessant.

For anyone travelling to Southern Brittany, this page may be useful, however, please refer to the Featherstone West France Cruising Companion (2nd edition) for more detailed information, especially of travelling by yacht.


Having studied the various tidal atlases, the slack water for the passages appear to be as follows:

Chenal du Four – High water Brest to HW +30mins and High water Brest +5.5 hours

We went past the Le Four lighthouse travelling South at HW Brest +5.5 hours and there was still some tide running.

See… with useful marks

As well as the waves and tides, there are often fog banks caused by the meeting of the currents

Raz de Sein – High water Brest -1 hour and High water Brest +5.5 hours. Slack water lasts for around 30mins

We arrived at the Raz de Sein at HW +5.5 hours and there was still a fair tide running to the North with overfalls. On our return journey, we were at the Raz de Sein at HW Brest + 4.25 hours and it was flat. Anyone have any experience they can share?

The following site provides useful waypoints and information on the area –…

This provides much the same information including the Raz de Sein –… . The diagrams the site produced are particularly helpful.

While discussing passages – the Sailing Almanac’s diagram of the Ile de Batz is also very helpful. Remember, only go through there on half tide up.…