It shouldn't be much of a surprize in Japan: where there's hot water enriched with minerals, there's people enjoying it somehow. Foot baths are extremely common in such places, and this is a basic foot bath, where you can just go down some stairs and step into the warm river. The temperature is comfortable, but the sand is black and very rough.
taken on 18 August 2017, 15:13
location: Noboribetsu Onsen in Noboribetsu, Hokkaidō, Japan