Oumijima Kankō Kisen

From the small port at Nagato on the Sea of Japan coast, whale-shaped boats take visitors on a circuit through the sea caves and rock tunnels of Oumijima island. The boats pass through narrow passages where the ceiling drops low and the water glows with reflected light. Artificial blowholes installed along the route shoot jets of water in imitation of the real thing, which is surprising the first time. The circuit takes about thirty minutes. The island's geology, shaped by centuries of wave action into arches and chambers, is genuinely unusual. It's a short excursion, best combined with a visit to Motonosumi Shrine nearby for a full morning.