A water barrier is a structure that is used to prevent the flow of water. TARP, DAM, MOAT, LEVEE, DIKE, and MILLDAM are all types of water barriers. A tarp is a waterproof sheet or cover that is used to protect against water. A DAM is a barrier built across a river or stream to hold back water. A MOAT is a deep, wide ditch that is filled with water and is usually found around castles. A LEVEE is an embankment built along a river or stream to prevent flooding. A DIKE is a wall or embankment built to prevent flooding. A MILLDAM is a DAM built to provide power for a mill.