モッタ海岸温泉 is a hot spring town in Hokkaido, Japan. Officially the water is classed as chloride spring and radioactive spring.
Salty water. The salt leaves a thin film on the skin, so you stay warm well after leaving the bath.
Contains trace radon that leaves the water quickly. Also called radium or radon springs.
Planning a first soak? Read how an onsen stay works, and what to do if you have tattoos.