In Chilkoot Inlet, along the SE end of Chilkat Peninsula, in Tongass NF, 4 mi. S of Battery Point and 22 mi. S of Skagway, Coast Mts. 1 mile long.
Local name reported by U.S. Geological Survey (USGS) in 1952. It was published in 1923 as "Flat Bay" on International Boundary Commission (IBC) Sheet 9 (1951 atlas). According to E. C. Robertson the name "Mud Bay" is how commonly used.