Marco Island is a city located in Collier County, Florida. It is situated on an island of the same name in the Gulf of Mexico off the coast of Southwest Florida. AMELIA Island is a barrier island located off the coast of northeastern Florida. It is the southernmost of the Sea Islands, a chain of barrier islands that stretches along the east coast of the United States from South Carolina to Florida. Sanibel Island is a barrier island located off the southwest coast of Florida. It is known for its beautiful beaches and wildlife refuges, and is a popular tourist destination.