This is one of the most beautiful things I have ever seen.
The "Grüner See" (engl. Green Lake) is situated in upper styria, austria (see geotag). It is amazingly beautiful because of its deep green/blue colour and the surrounding alpine scenery. The lake itself dries up in autumn but fills up with melting water. The water itself of the lake is extremely pure, like glass. The colour is a result of light refraction.
Here's the poster's description:
"The night before there seemed to be heavy rain and too much of the pollen were flushed in the water and were floating. So the visibility could be much better, i´ve missed the „crystal clear water. You have to know the Green Lake is famous for its clear water. The good thing for this day was the water level with 9,40m. Spring flowers, plants, benches, hiking trails were below the surface. And i have found out when its the best time during the two to three months "flood" to get in the water - i was to early in this season. Altough the water temperature was between 5 and 6 degrees Celcius i did two dives (85 and 96 minutes long)
My face was well frozen, i can hardly speak afterwards. I hoped this procedure kept my face young and skintight. After watching the footage it seemed to be different."