Sable (Island)

I can find no record of an island of this name off the coast of France (or anywhere else in France).

Sable is actually French for 'sand' (as well as a small Russian carnivore, prized for its fur, and the Heraldic term for the colour black), but the only island of that name that I could find is a thin, crescent–shaped island (little more than a 42–kilometre sand bar) off the coast of Nova Scotia (i.e. Canada).

You can discover eleven fascinating facts about Sable Island here. One of them is that it's home to about 500 feral horses, and no one knows how they (or their ancestors) got there.

The question setter was maybe thinking of Les Sables–d'Olonne, which is a seaside town on the Bay Of Biscay. But there is no island there that's deemed worthy of mention on Wikipedia – or anywhere else on the Internet as far as I can make out.