Birds can be seen on the beaches, the causeway islands and the reserves, including J. N. Ding Darling National Wildlife Refuge. Common sights include pelicans, herons, egrets, and anhingas, as well as the more common shorebirds like terns, sandpipers, and of course seagulls. The rare American crocodile has been been seen at the refuge as well.
Plants on the island include the native sea grape, sea oats, mangroves, several types of palm tree, and the non-native Australian pine.
Seashells often found include coquinas, scallops, and other clams, and sometimes whelks, sand dollars, and other deeper-water mollusks, both univalve and bivalve.
The city of Sanibel, Florida incorporates the entire island, with most of the town proper at the east end of the island.