accumulations algae attached clinging coastline color colour covered ebb-and-flood ebb-and-flow filamentous green holdfasts layers levels light low-tide ocean pounding rocks rocky rough sea seashore seaside seaweed shadows shapes shore shoreline slimy slippery spray sticking stones stony stuck sunlight sunshine surf surge surging tidal tide tides velvety water waves wet aquamarine aquatic blue fish giant kelp marine natural nature protection school shelter shoal bare coast England exposed Great Britain kent landscape low mollusc mussel rock rockpool shellfish sky stone winkle chalk cliff erode erosion face beach Pembrokeshire rockpools sand united kingdom wales welsh home house village animal background bivalve seashell shell texture