The Mesoamerican Barrier Reef System (MBRS), also popularly known as the Great Mayan Reef or Great Maya Reef, is a marine region that stretches over 1,000 kilometres (620 mi) from Isla Contoy at the tip of the Yucatán Peninsula down to Belize, Guatemala and the Bay Islands of Honduras.
The reef system includes various protected areas and parks including the Belize Barrier Reef, Arrecifes de Cozumel National Park, Hol Chan Marine Reserve (Belize), Sian Ka'an biosphere reserve, and the Cayos Cochinos Marine Park.
Belize's coastline, including the Belize Barrier Reef, is home to approximately 30% of the Mesoamerican Barrier Reef System.
The reef system extends along the coast of four countries: Mexico, Belize, Guatemala, and Honduras.
According to en.wikipedia