New York Times Bestseller! From bestselling author Susan Casey, an awe-inspiring portrait of the mysterious world beneath the waves, and the men and women who seek to uncover its secrets, An irresistible mix of splendid scholarship, heart-stopping adventure writing, and vivid, visceral prose." Sy Montgomery, New York Times best-selling author of The Soul of an Octopus For all of human history, the deep ocean has been a source of wonder and terror, an unknown realm that evoked a singular, compelling question- What's down there? Unable to answer this for centuries, people believed the deep was a sinister realm of fiendish creatures and deadly peril. But now, cutting-edge technologies allow scientists and explorers to dive miles beneath the surface, and we are beginning to understand this strange and exotic underworld- A place of soaring mountains, smoldering volcanoes, and valleys 7,000 feet deeper than Everest is high, where tectonic plates collide and separate, and extraordinary life forms operate under different rules. Far from a dark void, the deep is a vibrant realm that's home to pink gelatinous predators and shimmering creatures a hundred feet long and ancient animals with glass skeletons and sharks that live for half a millennium among countless other marvels. Susan Casey is our premiere chronicler of the aquatic world.