Boat communities are autonomous. Mergui boat communities are under the nominal direction of a headman who provides some amount of leadership to boat groups' movements and activities. Among some Riau-Lingga and Billiton groups, headmen had more than nominal authority. Adjacent dominant cultures sometimes imposed community leaders, so office titles vary depending on the dominant culture. Malay lords of Johor and later Binton and Lingga forced Riau-Lingga sea nomads to become their feudal vassals, calling them Orang Rayat ("sea subjects") and persuading the sea people to perform services, including pirating coastal villages and boats.