cockel shells clinging to beach rock at low tide

beach clam clams clinging close coastal cockel cockles cornwall crustacean food low macro mussel mussels rock rocks sea seafood shells shore south sticking stone sunlight tide west strong sheltered nature shallow waters tidal water cardiidae sessile ocean impermeable cockle sandy attached rounded edible detritus hermaphroditic substrate encrusters heart-shaped acorn barnacles calcite marine beaches radial bivalve saltwater stalk suspension feeders molluscs plankton bay hard