Shikinejima

The tide decides much of the day here. At Shikinejima, certain baths appear and disappear with the sea: Yamadachi Onsen sits submerged except at spring tides, and the open-air pools at Jinata Onsen, set into the coastal rocks, rinse themselves clean twice a day. The cliffs of rhyolite that ring the island make most of the shoreline unapproachable; life concentrates around the small harbors of Nobushi and Kohama, where the ferries from Takeshiba and Shimoda put in.

Roughly five hundred and fifty people live on a few square kilometers of volcanic stone. The rhythm is not picturesque so much as practical — fishermen, the small museum holding old maps of the island, the modest indoor bath at Ikoi-no-ie where islanders and visitors share the same warm water at a flat fee. Ashitsuki Onsen, locally called the "surgical bath," is treated as everyday medicine rather than spectacle. Matsugashita Miyabi-yu, free and beside the fishing port, is somewhere people sit after work.

What distinguishes this island from its larger neighbor Niijima is the scale and the geography: a closer-knit settlement, a coastline of pockets and crevices rather than long beaches, and a hot-spring culture that exists outdoors, in the rocks, beneath an Izu-Hakone-Fuji park sky. To stay any length of time is to learn the tide table — to read the sea the way one reads a train schedule elsewhere.