The clearest lake in the world is blue lagoon in Nelson, the South Island of New Zealand. It is reported that BlueLake, a blue lagoon, is located in Nelson Lake National Park and is by far the clearest natural water body. The water in the Blue Lagoon mainly comes from Lake Constance.

Near Nelson, the South Island city of New Zealand, there is one of the clearest lakes in the world, Tasman blue lagoon, which is located in Nelson Lake National Park in New Zealand. According to the scientific test conducted by NIWA, the Blue Lagoon is the clearest natural water body known to mankind. The visibility in the blue lagoon is as high as 80 meters, which means that the optical transparency of the blue lagoon is almost comparable to that of distilled water.