Answer:
Without question, Sanibel is considered the top shelling beach in the United States. This is due, in large part, to the east-west orientation of the island. It acts as a large shelf, collecting a tremendous variety of shells and other sealife. Over 400 shell species have been collected on Sanibel. Lighthouse Beach is an excellent place to do the "Sanibel Stoop" as you wade into low tide waters or scan the high tide line for treasures.
Northeast Florida is also a great area for shelling and finding sharks teeth. Jacksonville Beach,nearby Fernandina Beach and Ft. Clinch State Park are all great beaches to explore.