Ellie Harrison and Matt Baker head for South Wales' Gower Peninsula. Ellie visits Swansea Docks to see how its once filthy waters are now so clean that mussels thrive there. And she finds out how little yellow fishes are helping people flush their waste water down the right pipes. Matt joins the divers pulling tonnes of waste a year out of the waters off the peninsular, before hitting dry land to hook up with the volunteers keeping its beaches pristine.Adam explores the threat to livestock from nuisance dogs, and John Craven reveals the final twelve photographs to make it into next year's Countryfile calendar.