The park's coastline contains a biologically-important zone, wherein salt tidal marshlands meet the Gulf waters. These marshlands formed when silt from the Sabine River delta was carried down the beach by longshore currents. The park offers a marshlands airboat tour during the spring, summer, and fall. Tours are by advance reservation only, last approximately one hour, and fees apply. Airboat tours and canoe rentals are dependent on marsh water level and weather conditions.
Fishing is permitted from dawn to dusk.
Swimming is not permitted in the marshlands area, as alligators are present. The park is a prime wintering area for a variety of waterfowl common to the Texas Coast. Abundant wetlands wildlife include the American alligator, mink, nutria, raccoon, rabbit, opossum, skunk, rare river otter, and muskrat. The park's lakes and bayous are important areas for white and brown shrimp, crabs, and various sport fishes. The marshland waters, rich with abundant plankton and decomposing organic matter, provide fertile nursery grounds for aquatic life and are essential for the productivity of marine fisheries and migratory waterfowl.