Analysis of core and clam-shell samples from Sabine Lake, a lake estuary, and adjacent parts of the Gulf of Mexico, a nearshore neritic environment, shows that the character of the sediments is a poor criterion for differentiating the two environments. Wet sediments from both environments are mainly grayish to blackish, soft, very fine sandy and silty mud or silty and clayey mud, containing variable amounts of shell and plant material; very fine sand and fine sand are locally present. When dry, the sediments are lighter gray or black. Silt is dominant in both environments; very fine sand and sand rank second. Sorting is poor.