A dazzling and ambitious history of the pre-Columbian Atlantic seas, Ocean is a story that begins with the formation of the mid-Atlantic ridge some 200 million years ago and ends with the Castilian conquest of the Canary Islands in the fifteenth century, providing a template for the methods used by the Spanish in their colonization of the New World.

John Haywood argues that the perception of Atlantic history beginning with the first voyage of the celebrated navigator Christopher Columbus is a mistaken one, and that the seafaring and shipbuilding skills that enabled European global exploration and expansion did not arrive fully formed in the fifteenth century, but instead were learned over centuries and millennia in the Atlantic and its peripheral seas. The pre-Columbian history of the Atlantic is the story of how Europeans learned to master the oceans. This story is key to understanding why it was Europeans, and not any of the world's other seafaring peoples, who "discovered" the world.

Informed by the author's travels around the Atlantic Ocean, Ocean is an in-depth history of a neglected subject, fusing geology, geography, mythology, developing maritime technologies, and the early history of exploration to narrate an enthralling story—one which lies at the very heart of Europe's modern history and its relationship with the world.