Riverine communities or fishing villages are one of the major types of village communities in Cambodia. They tend to be built in concentrated clusters on the banks along main rivers down to and including the shore and flood plains. These communities are characterized by a mixed economy; they are self-sufficient in rice and fish, and their diets are supplemented by seasonal market produce. Floating villages, which are mainly found at the mouths of the major rivers where they empty into Tonle Sap, represent another major type of village community in Cambodia. These communities are characterized by self-subsistence and are specialized in fishing activities. Surplus catch is used to purchase other essential foodstuffs and tools. Inhabitants live on moveable boathouses grouped into tight clusters. They maintain their position by moving seasonally with the rise and fall of the level of the lake. The village composition of these floating communities is more loosely structured than that of subsistence farmers on the plains. Their ethnic composition is quite varied, but the majority are Khmer and Vietnamese, with some Cham.