Physical characteristic :
The Blue Coast is situated on the Nerthe massif, made up of sedimentary rocks of varied origin, secondary and tertiary. Bathymetry and underwater topography follow the landform and present a wide variety of aspects: steep falls to the east, rocky chaos and scree. The underwater relief softens to the west, with extensive sloping plateaus and sandy beaches. There are several submerged caves on the Blue Coast (falling Méjean, cliff Méjean, Vesse, Le Chinois, habitat of the «dark caves» and «semi-obscure caves»). The high frequency of winds (NO regime of Mistral and East) enhances the existence of strong alternating currents of East and West. They carry very plankton-rich waters, leading to high productivity and a wealth of fish.