Some ~1500 PALACE float temperature profiles obtained throughout the Gulf of Mexico between April 1998 and March 2002 indicate that temperature inversions are rather common. Most are seen near the surface, but some are seen at essentially all depths down to the deepest measurement at about 1000 m. The inversions are associated with layers of relatively cool, and presumed fresher, riverine and coastal waters. Most are attributed to the Mississippi River and Mexican rivers discharging into the Campeche Bay, and a few are thought to have drifted in from the Caribbean Sea.