Hot Water Beach

For two hours either side of low tide on this beach on the Coromandel peninsula the hot springs beneath the sand are accessible. You can stand and let your feet sink in until the sandy water is too hot to bear (it's 64°C) or dig a pool to be filled by spring water then let in enough sea water to cool it to spa temperature.

Which explains why these 70 strangers are congregating in a very small area of a large, otherwise empty, sandy beach.