beach builders' rubble coast coastline color colored colors colour coloured colours dumped growing growth layers levels low tide mangroves natural ocean outcrop pebbles plants pollution receding tide rock formations rocks rocky rough rubble sand sea seashore seaside shade shadows shapes shore shoreline Sizes stones stony sunlight sunshine tidal tides variety waste water waterline adults children distance distant expanse families light open area people recreation relaxing strolling sunset tide waders wading walking accumulations algae attached clinging covered ebb-and-flood ebb-and-flow filamentous green holdfasts low-tide pounding seaweed slimy slippery spray sticking stuck surf surge surging velvety waves wet footprints industrial activity industrial area Jetty prints receding sandy ships blue grey sky skyline terrain horizon