Plage Grande Mer, Mediterranean beach in Cassis, France.

Plage Grande Mer is the main beach of Cassis, a pebbled shore at the end of the Avenue du Docteur Yves Bourdes, where the town meets the sea below the Cap Canaille cliffs. The beach is divided into a free public section and a private concession with sun loungers, and the limestone seabed drops gently, giving bathers a wide shallow entry before deeper water.

The beach sits beneath a medieval castle that defended the town from the 13th century onward. This fortification shaped Cassis as a protected harbor for local trade and fishing.

The beach is named after the sea it faces, "Grande Mer" meaning the open Mediterranean. Fishermen from Cassis still land their catch at the port beside the beach, and the morning sale of fish shapes the daily rhythm of the waterfront.

Plage Grande Mer lies at the end of the Cassis waterfront, a short walk from the port along Avenue de l'Amiral Ganteaume. The pebble shore shelves gently, so entry is easy, but the stones make water shoes useful. Showers and restrooms stand on site, and lifeguards watch the swimming area from May to September; outside that season the water is cooler and swimming is unsupervised.

Underground freshwater springs mix with Mediterranean currents beneath the beach, keeping water temperature surprisingly stable throughout the year. This natural feature makes swimming enjoyable even in cooler months.