Kate Humble presents a celebration of the UK's surprising and beautiful marine life and takes an in-depth look at the issues affecting our coastal waters. From Cornwall to Scotland Kate reveals breathtaking marine animals - dolphins, otters, and colourful local fish that look almost tropical, and gets wet when she swims with the huge but gentle basking shark - Britain's biggest fish. Kate also finds out what we can all do to help conserve and enjoy this wildlife and how simple changes in our appetite for fish and chips could save the UK's fishing industry. Good news comes in the form of a new Marine Bill which could prove the most significant turning point for our UK sea life.