Okishima

Okishima is a beginner-friendly freshwater dive site in Lake Biwa, Japan's largest lake, located in Shiga Prefecture near Kyoto. This unique inland diving experience takes divers into the waters surrounding Okishima island, the only inhabited island on a freshwater lake in Japan. The lake floor features volcanic rock formations and sandy substrates reaching 10 meters, with visibility varying seasonally. Lake Biwa's ancient origins — it is one of the world's oldest lakes — have produced endemic species found nowhere else, including the Biwa catfish and various unique crustaceans. Freshwater sponges, aquatic plants, and colonies of freshwater mussels create underwater gardens on the rocky substrate. The cultural and ecological significance of diving in this 4-million-year-old lake adds a dimension beyond typical marine diving, offering a fascinating window into freshwater ecology and Japan's natural heritage.