The huge lake called "Tonle Sap" near Siem Reap was the main trading highway of the area for centuries. The water level varies dramatically from high (when the snows of the Himalayas melt) to low (at the end of the dry season.) Fishermen live in "floating villages" to follow the fish at all seasons. Most have rice paddys too, to provide the other staple of their diet. In this photo you can see boat hulls under the houses.