Goose Island State Park is located at the southern tip of Lamar Peninsula amid the bays and estuaries of the Texas Gulf Coastal Bend. The mainland portion of the park is comprised of a live oak, red bay woods that also contains yaupon holly, American beautyberry, coralbean and wax myrtle. Also on the mainland is a portion of tallgrass prairie consisting of bushy bluestem and saltgrass. Wildlife observation and photography opportunities abound; wildlife present in the park includes white-tailed deer, raccoons, armadillos, foxes, squirrels, cottontail rabbits and over 300 varieties of birds. The endangered whooping crane feeds on berries and blue crabs found in the coastal wetlands around Goose Island State Park.
The island portion of the park is an oyster shell island consisting of a shell ridge and marshland. Plants on the shell ridge portion of the island include sea-ox-eye daisy, wolfberry, sea purslane, baccharis and seashore dropseed grass. The marsh at Goose Island includes smooth cordgrass, marsh-hay cordgrass, saltgrass, saltwort and glasswort. The bays around Goose Island are filled with seagrass beds and oyster reefs. Red drum, speckled trout and flounder are just a few of the fish that live in the bays around the island.