Every year the Mekong River backs up and increases the size of Tonle Sap, the largest lake in Southeast Asia, from 2700 to 16000 square km.  A prime breeding ground for fish, Tonle Sap is responsible for 75% of Cambodia's inland fish catch, and 60% of it's protein intake.  Unfortunately, pollution (you can see in green), and planned dams along the Mekong threaten the lake, and the people who depend on it.

I was fortunate enough to travel along the shores of the lake, take a boat onto the lake, and also fly over in an ultralight aircraft to see it from all angles.  This photo was taken from high above one of the floating villages.