I think what you're talking about is the pictures that have been doing the rounds on social media networks like Facebook, depicting dead animals frozen in place as if turned to stone by some modern day Medusa.
The haunting pictures are actually the work of artist Nick Brandt, but the lake does really exist - and there is a biological explanation as to how these animals were turned to stone:
The lake in question is called Lake Natron, and is located in Tanzania - close to the Kenyan border.
The mystery behind the animals turning to stone is actually pretty simple:
Because of its reflective surface, all sorts of birds or animals accidentally fly straight into the lake.
Because the water has such high carbonation and salt levels, anything that enters its waters emerges and immediately dries up and becomes encased and calcifies. This preserves them for ever - just like stone statues!