A bell buoy, located to the south of Mixon Shoal in 11 fathoms, is shown on historic charts. Contemporary Sailing Directions provide confirmation - ' A black bell buoy marks the southern elbow, of Mixon shoal; it lies in 10 fathoms with Porth Eynon and Oxwich heads in line, W by N 1/2 N, Kilvey old mill NE 1/4 E; and Mumbles lighthouse NE 1/2 N'

Sources include:
Admiralty; 1884, Sailing Directions for the Bristol Channel, 4th Ed, pg102
Historic Admiralty Chart 1076-B8, RCAHMW Digital Collections sourced from the UK Hydrographic Office and published in 1886
Historic Admiralty Chart 1161-C1, RCAHMW Digital Collections sourced from UK Hydrographic Office and published in 1885

Maritime Officer, RCAHMW, August 2014.