Kochi Prefecture dive sites

The nearest major city is Kochi on Shikoku island, accessible by domestic flights from Tokyo, Osaka, and Fukuoka. From Kochi, drive approximately three hours west along the coast to Otsuki, the mainland town connected to Kashiwajima by a bridge. Alternatively, take a train to Sukumo and arrange local transport. Several dive shops operate on the island and in Otsuki, most requiring advance reservations. The journey is part of exploring Shikoku's remote and beautiful southwestern coast, one of Japan's least-visited regions.

Kashiwajima sits at the intersection of the warm Kuroshio Current and cooler temperate waters, creating conditions where tropical and temperate nudibranch species overlap. Over 200 species have been documented, making it one of the highest nudibranch diversities anywhere in the Western Pacific. The rocky reef substrate with its diverse algae, sponge, and hydroid communities provides habitat for species that do not co-occur elsewhere. Dedicated nudibranch guides can find 30 to 40 species in a single dive during peak season.

Scalloped hammerhead sharks are encountered at Kashiwajima's deeper sites, primarily between August and October when water temperatures peak. The sharks tend to appear in the blue water off the reef edges at depths of 25 to 35 metres, sometimes in small schools. Sightings are not guaranteed and depend on current, visibility, and seasonal patterns. The hammerhead season coincides with the best overall diving conditions including warmest water and highest visibility, making it the peak period for visiting divers.