Salt Lakes Burgas, Bulgaria
Here it is where the salt (we are using all the days to eat) coming from. If you are lucky to have a bad weather you will have as a result this kind of picture!
The water is natural red because it is a salt lake. And I guess that it depends on the angle of incidence of light and the position of making picture. It is also possible to depend from the % of salinity of the water on that moment. By the way looking to the water on the other part of the lake it did not look so red, so probably the first assumption is more true.
Take a look on the map right here and you will see that there are many other lakes that have red color!