algae beach bladderwrack coastline Cornish cornwall England english Great Britain low natural nature ocean rocks sand sandy sea seaweed shore summer tide water waves alien Carpobrotus edulis coast dune ecology flora flowers habitat hottentot fig ice plant introduction invasive pink plant soft Spain wild holiday leisure resort rock surf vacation yellow bay cliffs cove hill low tide river sheltered breakwater fun groyne horizon kent landscape sailboard sky wave blue enjoyment family holidaymakers pleasure active beautiful chile green lake mountain pucon smoke snow south stone tree trees villarica volcan volcanic volcano white beauty clear islands Maddalena mediterranean refreshing ripple Sardinia shoreline