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.


The slack water for the passages are as follows:

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

See… with useful marks

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

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.…