Map of the Townsville reefs in the central Great Barrier Reef. Grey “×” symbols represent the locations of receivers within the Townsville reefs region, dotted grey lines indicate reef boundaries, dotted dark grey polygons represent the drying reef, light grey lines represent bathymetry within the region. Top right inset indicates location of the Townsville reefs along the Australian coast and bottom left insets indicate the location of the receivers on (a) Helix Reef, (b) Wheeler Reef and (c) Lodestone Reef. Light grey lines within the insets represent the 20-m contour line. Bathymetry data generated from Beaman .