Discovery Bay, uninc. town (1990 pop. 5,351), Contra Costa co., W Calif., planned residential community 13 mi/21 km SE of Antioch, 5 mi/8 km ESE of Brentwood; 37°55'N 121°36'W. Subdivision built entirely on man-made necks of land in man-made Discovery Bay, on Indian Slough, giving all residences water access.