This time on Britain's Secret Seas, the team set out to explore the waters off our eastern coastline, which are constantly pounded by the raw power of the waves. These are the shallowest waters off our shores but over the centuries they have been some of our most productive, providing oil and gas as well as fish for our tables. But things are changing in the North Sea and our team discover a sea full of surprises. On the Farne Islands, they come face to face with England's largest colony of grey seals to find out what makes them such extraordinary divers and successful hunters. Grey seals can dive for over forty minutes on a single breath - the team find out how they do it and why they seem to be coping with the changing conditions on the east coast far better than the harbour seal. Elsewhere, Frank looks at the newest form of energy in the North Sea, at a wind farm off the Norfolk coast, and Tooni examines what effect the wind turbines are having on marine life. Paul uncovers the intriguing history of light vessels among the sandbanks of the Thames Estuary; and Tooni gets to the bottom of a bumper lobster harvest in the port of Bridlington. Paul dives with a shoal of fish that soon transform into a school when he starts to behave as if he were a predator. To find out how they are able to achieve such synchronised motion and why they suddenly change direction, he joins a scientist who has created a plastic imposter - Robofish.