Okayama · Tamano & Uno Port
Tamano Onsen (Diamond Setouchi Marine Hotel)
たまの温泉（ダイヤモンド瀬戸内マリンホテル）
A natural spring inside the Diamond Setouchi Marine Hotel on Shibukawa Beach in Tamano. Its weakly radioactive calcium-sodium chloride spring fills an open-air bath overlooking the Seto Inland Sea, available for day bathing.
- Price (adult)
- ¥1,000
- Hours
- 15:00–21:00 (last entry 20:30)
- Closed
- Open year-round
- Access
- 2-12-1 Shibukawa, Tamano, Okayama (inside the Diamond Setouchi Marine Hotel). About 25 minutes by car from Kojima IC on the Seto-Chuo Expressway, or about 80 minutes by express bus from JR Okayama Station to Shibukawa Marine Hotel.
- Water type
- Radon spring
- Tattoos
- Ask ahead
- Phone
- 0863-81-2111
- Official site
- okayama-kanko.jp ↗
- Open in Google Maps
- Google Maps ↗
Essentials
Find a stay on Trip.com
Search and book accommodation across Japan on Trip.com. Day-use bathing needs no booking.
Opens partner booking site (affiliate)
Why go
- A weakly radioactive calcium-sodium chloride spring (pH 8.7, weakly alkaline, colorless)
- An open-air bath overlooking the Seto Inland Sea and Shibukawa Beach, plus an indoor bath
- Day bathing: adults 1,000 yen, children 450 yen; 15:00-21:00 (last entry 20:30)
About this onsen
A weakly radioactive calcium-sodium chloride spring. Its open-air bath overlooks the Seto Inland Sea and Shibukawa Beach, and the hotel accepts day bathers from 15:00.
Good to know
Day bathing runs 15:00-21:00 (last entry 20:30) at 1,000 yen for adults. The window is short, so it is worth checking the hours before you go.
Before you go
- No official tattoo policy is published — ask at reception.
- Ryokan day-use hours are limited and may be suspended in peak season — phone the same morning.
- Last entry is 30–60 minutes before closing.
Features
Mood & scenery
Convenience
Amenities
✔ Verified operating: 2026-10 Operating status and rates cross-checked against the official site and onsen guides (full source notes in Japanese on the JA page)
Prices and hours change. Check official sources before visiting.
More in this area
Yubara Onsen Sunayu
A natural open-air bath on the Asahi River gravel bed right below Yubara Dam, where water bubbles up through the riverbed itself — ranked the 'western grand champion' of Japan's rotenburo. Three pools at different temperatures; mixed, free and open 24 hours. Only a simple changing hut, so women are advised to wear a bathing garment (sold and rented in town). Closed Wednesday mornings for cleaning. Photography strictly forbidden.
Yunogo Onsen Sagi Onsen-kan
The source bath of Yunogo Onsen, where legend says the monk Ennin found an egret healing its wounds some 1,200 years ago. One of the three famed Mimasaka hot springs, an hour by car from Okayama. The town-run bathhouse charges ¥960 for indoor and open-air baths across two bathing wings linked by a moving walkway, alternating daily. Open 8:00–21:00; the 'all-day rest' plan lets you come and go until closing. Bring your own food.
Okutsu Onsen Hanabijin-no-Sato
A town-run day spa at Okutsu Onsen, one of the three Mimasaka hot springs and famous for the autumn colours of Okutsu Gorge. The airy, high-ceilinged main bath holds pH 9-plus alkaline 'beauty water', with a rotenburo, family baths and sauna. ¥880, 10:00–19:00, closed Thursdays. The gorge trail is within walking distance, so it fills up after leaf-viewing in autumn. Forty minutes by car from Tsuyama.
