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洞爺温泉 is a hot spring town in Hokkaido, Japan. The water leaves the ground at 60°C, hot. Officially the water is classed as simple spring, chloride spring and sulfate spring.
Mild and low in dissolved minerals. Usually clear and gentle on the skin, which is why these baths are often recommended for first-timers.
Salty water. The salt leaves a thin film on the skin, so you stay warm well after leaving the bath.
Clear water with a faintly bitter taste. Known for holding heat.
Figures from the town's Japanese Wikipedia article.
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