Paul Rose, Tooni Mahto, and Frank Pope explore Britain’s western waters. They look at Britain’s largest fish, the basking shark, off the coast of Cornwall, and giant spiny crabs off the coast of South Wales. They assess the merits of the Lundy Island’s ‘No Take Zone’ and whether it could be used as a template for a nationwide network of marine nature reserves around the UK. The team also examine how we balance the needs of marine life with those of people when the two come into conflict when they assess the legacy of Britain’s worst ecological disaster to affect our shores; the 1967 Torey Canyon oil tanker spill.

The team explore the wild seas around Scotland. They travel to Bass Rock, one of the largest Gannet colonies in the world, to determine why when most British seabird populations are in decline, the Northern Gannet is bucking the trend. Tooni goes in search of the bottlenose dolphin to find out why dolphins have unique signature whistles. There are over 25000 wrecks around the British Isles, which are a rich archaeological record of our maritime heritage. Sadly, they are being damaged by trawlers, souvenir hunters and the forces of nature. Frank and Paul Rose go to the Sound of Mull, to see first-hand what can be done to preserve the history locked away in these relics.

The team set out to explore the waters off Britain’s eastern coastline, which are constantly pounded by the raw power of the waves. These are the shallowest waters off Britain’s 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. 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.

In the final programme of the series, the team explore Britain’s busy southern shores. As one of the world's busiest shipping lanes, the southern seas are littered with wrecks. Outside Poole harbour, the team join an archaeological excavation of a mysterious 17th century ship which is one of the most important underwater discoveries since the Mary Rose. The team also examine how we balance the needs of marine life with those of people when the two come into conflict.