The island of Sensui-jima is just five minutes across the water from Tomo-no-ura town. There's a walking path that hugs the coast, passing by interesting rock formations and offering views across the water, especially lovely at sunset. After a stroll, drop into Kokuminshukusha Sensui-jima , where non-guests can take a soak in the range of baths for ¥525 (from 10am to 9pm).
The ferry that shuttles passengers across to the island is modelled on the Edo-era steamboat Iroha Maru .
There are no English signs on the island, so check with the tourist office in Tomo-no-ura town if you have specific questions on where to go. The ferry runs to the island every 20 minutes from early morning to 9.30pm.