All of the Earth's ocean, from the equator to the poles, is a single engine powered by sunlight - a blue machine. From the ancient Polynesians who navigated the Pacific by reading the waves, to permanent residents of the deep such as the Greenland shark, which can live for hundreds of years, this book explores the vast currents, invisible ocean walls and underwater waterfalls that all have their place in the ocean's complex, interlinked system. Helen Czerski is a physicist at UCL and a regular TV presenter.