Boats on Tonle Sap, Cambodia's huge freshwater lake. During the dry season from November to May, the lake is fairly shallow – only about one meter deep – allowing boats to be poled. During the monsoon season, waters from the flooding Mekong River back up raising the lake depth to about nine meters. This annual pulsing over a large floodplain brings in high sediment and nutrient fluxes allowing for rich aquatic diversity. Tonle Sap is one of the most productive inland fisheries in the world.