South Puget Sound is the southern reaches of Puget Sound in Southwest Washington, in the United States' Pacific Northwest. It is one of five major basins encompassing the entire Sound, and the shallowest basin, with a mean depth of 37 meters (121 ft). Exact definitions of the region vary: the state's Department of Fish and Wildlife counts all of Puget Sound south of the Tacoma Narrows for fishing regulatory purposes. The same agency counts Mason, Jefferson, Kitsap, Pierce and Thurston Counties for wildlife management. The state's Department of Ecology defines a similar area south of Colvos Passage.