This artificial lake, which is located near the border of Drenthe and Friesland, is made by sand exploitation from the earth surface. There are some spots in the earth crust, such as this one in Drenthe, were the sand rich layer reaches the surface. And there is were you can find the companies who collect the sand with large sucking machines, wash it and sell it for multiple purposes.
The distinct turquoise colour of the lake is caused by sediments drifting in the water and often reflect the colour of the skies above.
For me, it was a location which was on my wish list for a while. The only thing I had to do was to wait for the right circumstances. The results are almost giving you the idea that these photos were taken on a tropical island.