Cozumel, a mostly undeveloped Mexican island in the Caribbean Sea, is a popular cruise ship port of call famed for its scuba diving. At Arrecifes de Cozumel National Park, divers can explore a section of the Mesoamerican Reef and Museo Subacuático de Arte’s submerged sculptures. Chankanaab is an eco park surrounding a lagoon with underwater caverns, home to dolphins, manatees and sea turtles.