algae blue brown coastline exposed green Lofoten Islands low natural nature norway norwegian ocean plants rockpools rocks sea seaweed shore strata tide water weed beach coast coastlines colors colours drop drops foam rock sand splash textures wave waves white black brooding cliff Cornish cornwall dark England english granite granitic Great Britain rocky stones view wild coastal face grass meadow surf low tide Molluscs mussels Mytilus seascape shellfish gray grey hills islands mountains mysterious northern peaks remote misty betray danger islet Pembrokeshire spray spume summer treacherous united kingdom wales welsh