What is de sein?

Some articles on de sein, sein, de:

Raz De Sein - Maritime Disasters
... French ships leaving Brest had several options, and the Raz de Sein was among them, so it was the scene of several important actions ... on 16 December 1796 the Séduisant was lost as the French invasion fleet transited the Raz de Sein at night in stormy weather in an attempt to avoid the British blockade ... found two days later with no apparent damage, roughly 15 km from the Île de Sein ...
Sein
... Sein can mean île de Sein, an island of Bretagne Île-de-Sein, a commune of Bretagne Raz de Sein, a stretch of water in Bretagne Sein, a character ...