Walking on a transparent frozen lake

In this amazing video you see  two guys hiking in the High Tatras Mountains, in Slovakia, this is when they come across a frozen lake with crystal clear ice.

The water is so transparent that they seem to be floating a few feet above the ground.  High Tatras Mountains are a mountain range along the border of northern Slovakia in the Prešov Region, and southern Poland. They are a range of the Tatra Mountains chain.