Shelling is one of the best things to do in Marco Island. The beaches of Marco Island Florida are famous for having some of the best shelling and attracts shell seekers from all over the world. Of all the beaches in the area, Keewaydin Island is one of the best kept secrets for shelling in southwest florida. Best Shelling in Marco Island, Florida Keewaydin Island Keewaydin Island is a barrier island located within the Rookery Bay National Estuarine Reserve. It is bordered by