The deep oceans are the last great frontier remaining on Earth. Humans have conquered the vast wilderness of the terrestrial surface, from the searing deserts and dark forests of the tropics to the icy polar regions. Today, anyone with enough ambition and money can travel upriver into the heart of the Borneo jungle, climb Mount Everest, or spend the night at the South Pole. But the oceans beyond the continental shelves remain forbidding, beyond...