Berwick Bay is the lower Atchafalaya River reach in Louisiana between Morgan City and Sixmile Lake, lying between Berwick on the west bank and Morgan City on the east. It serves as a busy waterway and a key crossing point for U.S. Route 90 and a Southern Pacific vertical lift bridge linking the two communities. Its significance extends across the region because this stretch gives its name to Vessel Traffic Service Berwick Bay, the Coast Guard system managing nearby waters, including major waterway junctions and tributary bayous. Narrow bridge openings and swift currents require one-way vessel movement, and direct traffic control makes the service unusual among Coast Guard vessel traffic services.