p.s At high tide it’s the sea, at low tide it’s the hot spring♨️ (5 photos)

This is "Hirauchi-Kaichu Onsen". It is located on an island called Yakushima, which belongs to Kagoshima Prefecture in Japan. "Kaichu" means in the sea, "Onsen" means hot spring♨️, and "Hirauchi" is the name of the place.