Complex sentence: The region covered is the Caribbean, its islands (most of which enclose the sea), and the surrounding coasts, as well as the southern part of the Gulf of Mexico, Florida, Central America, and the northern region of South America.
Split into simpler sentences: The region covered is the Caribbean, its islands (most of which enclose the sea), and the surrounding coasts. Also included is southern part of the Gulf of Mexico, Florida, Central America, and the northern region of South America.