La Barre-de-Monts hermelle reef revealed by low tides

During the September 2026 equinox tides, the receding sea at Fromentine beach in La Barre-de-Monts has revealed the local hermelle reef. This natural structure, formed by sand tubes created by tiny marine worms, is the second largest reef in Europe, following the one at Mont-Saint-Michel.

Guided walks organized by the Pays de Saint-Jean-de-Monts tourism office have allowed visitors to explore the biodiversity of the mudflats. These areas are noted for their role in carbon sequestration and providing nutrition for seabirds. Additionally, the reef acts as a natural barrier against marine erosion by breaking the force of waves and swells.