block boulder coast coastal coastline cracked eroded erosion fissure fractured Gower Great Britain littoral natural nature plant rock sea shore shoreline tide wales water betray blue cliff danger islet Pembrokeshire spray spume summer treacherous united kingdom waves welsh angry boisterous boulders green rocks rough big Cabo Girão drop enormous harbour high huge landscape large madeira ocean seascape sheer sudden tall village bay Cornish cornwall England english hillside surf power bracken plants view island isthmus rocky Skomer wild boat trawler