The Tonle Sap Lake is the largest fresh water in South East Asia. Its dimension changes depending on the monsoon and dry season. During raining season from June to October, the lake is filled by water flowing from the Mekong with 14 meters in depth and expands the surface of 10,000 square Kilometers. In dry season from November to May its size 3,000 square kilometers with two meters in depth and water flows out from the Lake to the Mekong, in and out flowing is the natural phenomenon occurrences. The flooded forest surrounding the edge of the lake is the best shelter and also very important for all kinds of fishes spawned and breeding babies. This lake providing many of biodiversities, over 300 species of fresh water fishes, as well as snakes, crocodiles, tortoises, turtles and otters. More than 100 varieties water birds including storks, pelicans, etc

The Lake is also an important commercial resource, providing more than half of the fish consumed in Cambodia.