From Cnut to D-Day: the history and science of the unceasing tide explored for the first time. Half of the world's population lives in coastal regions lapped by tidal waters. Yet how little most of us know about the tide. Our ability to predict and understand the tide depends on centuries of science, from the observations of Aristotle and the theories of Newton to today's supercomputer calculations. This story is punctuated here by notable tidal episodes in history, from Caesar's thwarted invasion of Britain to the catastrophic flooding of Venice, and interwoven with a rich folklore that continues to inspire art and literature today. With Aldersey-Williams as our guide to the most feared and celebrated tidal features on the planet, from the original maelstrøm in Scandinavia to the world's highest tides in Nova Scotia to the crumbling coast of East Anglia, the importance of the tide, and the way it has shaped - and will continue to shape - our civilization, becomes startlingly clear.