While human travel to and from Japan, surrounded as it is by the ocean, has been carried on via the sea since prehistoric times, most of our knowledge from those times up to when ancient history begins is based on archaeological surveys of terrestrial sites and research into early written records. An ocean-based perspective has been missing from historical research until now. We look forward to when progress in historical research into sites along coasts, underwater, and on islands produces a richer historical vision of Japan.