Introduction to Cozumel Island: Cozumel (Cozumel) is located east of the Yucatan Peninsula. It is the largest island in the Mexican Caribbean, 30 miles long and 10 miles wide. Cozumel is home to the largest coral reef system in the Western Hemisphere, and the entire island is made up of more than 40 dive sites, tropical fish, and a kaleidoscope of colorful coral reefs. The clear coast, azure waters, rare undersea plants and animals and the ancient monuments of San Gervasio are a unique sight not to be missed.