The Raz de Sein is a stretch of water located between the Isle of Sein and the Pointe du Raz in Finistère located in the Brittany region of France.
This tidal water is an essential passage for vessels wishing to pass between the Atlantic and the English Channel, because further west at high tide the Isle of Sein and its embankment stretch for more than thirty miles.
This is a very dangerous zone for navigation due to the violent sea currents from the tides (up to six knots during the spring tides). The current causes the sea to rise quickly, and it is recommended that heavy vessels should only attempt to cross this strait at still water during calmer conditions.
The Raz de Sein is bounded by the La Vieille and Petite Vieille lighthouses and by the shoreline of the île de Sein.
