As a boy growing up on California's coast, Robert Ballard was fascinated by marine geology and life underwater. While working for the U.S. Navy, he built his expertise in the new technology of submersibles, which served him well in later expeditions. In the 1970s, Ballard took part in several key discoveries in marine science, including direct proof of the theory of plate tectonics and the first sightings of hot water vents and colonies of unique organisms that surround them on the deep-sea floor. Ballard's most famous expedition found the remains of the Titanic. Read about the life and work of this undersea explorer who combs the deep for the answers to science's secrets.