South Bay is a section of Wachusett Reservoir accessible through Gates 6 to 17A along MA-70.

Wachusett Reservoir, along with the Quabbin Reservoir and Ware River, is an unfiltered source of high-quality water for the Massachusetts Water Resources Authority water supply system. The 65-billion-gallon reservoir covers 108 square miles with 37 miles of shoreline. Recreational activities are regulated and limited to protect 3 million people’s drinking water.