Breadcrumb Home Holding Tank Images to Hide http://ocean.si.edu/holding-tank/images-hide/mesoamerican-reef-regional-map Mesoamerican Reef Regional Map photo Mesoamerican Reef Regional Map (Courtesy Healthy Reefs For Healthy People Initiative) The Mesoamerican Reef extends over 600 miles (1000 km) through the waters of Mexico, Belize, Guatemala and Honduras and includes the Western Hemisphere’s longest barrier reef.