The term 'barrier water' refers to a type of water body that is separated from the main body of water by a physical barrier. This barrier can be a REEF, a GATE, a LEVEE, or a WEIR. A REEF is a ridge of rocks or coral that rises above the surface of the water. A GATE is a structure that can be opened and closed to control the flow of water. A LEVEE is an embankment built along the banks of a river to prevent flooding. A WEIR is a low dam built across a river to control the flow of water.