Hateruma Island is Japan's southernmost inhabited island and a remote boat-diving base for the Yaeyama area. The dives mix white-sand shallows on the northwest side with east-side drop-offs, so the island gives both easy scenery and more dramatic fishier water. It suits divers and freedivers who want very clear tropical water, but the logistics are remote and the day works best with a local operator and a calm sea. Expect standout visibility, coral, seahorses, tuna, hammerheads, and eagle rays.