O.C.G.A. § 36-1-2: Extent of jurisdiction of counties divided by water.

Whenever a stream of water is the boundary of a county, the jurisdiction of the county shall extend to the center of the main channel of the stream, provided that whenever a stream of water is the boundary of a county and such stream or a bank thereof is the boundary of the State of Georgia, the jurisdiction of the county shall extend to that point which is the boundary of the state.