One of the great scientific and archaeological feats of our time has been to cast light on the "eternal darkness" of the deep sea. In this personal account, Robert Ballard—discoverer of the Titanic—combines science, history, illustrations, and first-hand expedition stories to tell how twentieth-century explorers and new technologies opened the deep ocean. He covers pioneers (Beebe, Barton, the Piccards), the discovery of hydrothermal vents and black smokers, sea-floor spreading, development of ROVs and remote-operated techniques, and his searches for historic wrecks and trade routes, offering a richer understanding of earth science, marine biology, and the history of exploration.