Plage de l'Éventail, Saint-Malo

What Seaglassmap found here

The shore below the Saint-Malo ramparts, out towards Fort National, is the best-documented sea-glass ground in France. It only works at low water: the tide pulls back off a wide field of rock and coarse shingle, and the glass sits in the gaps between the stones. One French collector logged around a hundred pieces an hour here; a second, two years later, found lots of glass on the same walk out to the fort. Expect plenty of under-tumbled pieces you'll put back. The frosted ones are there, but you sort for them. Old dark "pirate" glass turns up, which fits a walled port that has been throwing bottles into this bay for centuries. Watch the tide: the causeway floods and the rocks go under. Take the glass, leave the pebbles: pocketing galets is a €1,500 offence in France, while sea glass is explicitly yours to keep.