Figure 130. Bathymetry derived from navigation charts in area of The Quicksands, Gulf of Mexico, shows locations of major navigational markers and reefs (from Shinn et al., 1990). The Marquesas-Quicksands ridge is demarcated by the 30-ft depth contour (10-m bedrock contour in Fig. 131 and on Bedrock Surface map). For navigational purposes, bathymetric data should be considered inaccurate in areas of shifting sands.