Donuzlav is the deepest lake in Crimea. Originally, it was a sea bay separated from the sea by a sand spit, which is 9 km long and 200-600 m wide. The lake is salty. It becomes so narrow and shallow in its upper part that it looks more like a river, where it is freshened by spring water. This is why aquatic and swamp plants, so unusual for Crimean valleys, grow in the upper part of Donuzlav.