Much of human history is hidden beneath the waves: Some 3,000,000 shipwrecks may rest on the world’s seabeds. But archaeologists had to rely on professional divers for scraps of information about these sites until the 1960s, when George Bass began to apply rigorous excavation techniques to underwater wrecks. Over the next half century, Bass led groundbreaking studies of Late Bronze Age (1600-1100 B.C.) shipwrecks off the coast of Turkey, along with sites from many other periods. Along the way, he transformed underwater archaeology from an amateur’s pastime to a modern scientific discipline. Those achievements earned him a National Medal of Science in 2002.