Chris investigates why the waters and coastlines of the UK are the most popular places in the world for two of our coastal species: the grey seal and the Manx shearwater. He also makes a stand for an animal that he considers much misunderstood - the British gull. And he meets two animals which have truly extraordinary ways of sensing Britain's coastal environments - the shore crab which finds its way around by smelling through its feet, and the bottlenose dolphin which can identify a fish at 200 paces in the pitch black, using echolocation.

• Chris Packham