Rodeo Lagoon is a coastal lagoon located in the Marin Headlands division of the Golden Gate National Recreation Area, which is in southern Marin County, California.[2] This brackish water body is separated from the Pacific Ocean by a sand bar that forms Rodeo Beach. Rodeo Lagoon empties into the Pacific Ocean when the water level reaches a high enough level to erode through the sand bar. This high water level usually occurs in the winter months.