Not quite right! The water is in fact naturally blue and naturally heated, but the pool itself is not natural. It’s created by the nearby power plant. If you come from the main road and enter from the main entrance you might never see the power plant itself, but if you explore the paths outside the lagoon, or keep an eye out from the road, you will definitely see it.
The power plant pumps heated water from the underground to run a turbine generating electricity. The water is then distributed through a heating exchange system to help provide heated water to the local municipality. Finally, some of the excess water is used to create the pool we know as the Blue Lagoon.
The pool water is around 37-39 degrees and changed every second day. It’s full of natural minerals claimed to have a healing effect.