One of Mexico’s biggest islands, Cozumel, lies 20 km (12 miles) from the mainland, and 60 km (36 mi) south of Cancun. It is a flat, limestone formation in the shape of a handgun, and sprinkled by tens of cenotes (water-filled holes), many with their own marine forms, which are an extra attraction for tourists and marine biologists who come to explore the island’s amazing offshore reefs.

Jacques Cousteau first promoted Cozumel in 1960, when he fingered Palancar at the island’s southern tip as one of the world’s best diving locations. He triggered a growth in tourist development, only curtailed in with the establishment of the National Marine Park in 1996: but the reefs were badly damaged by the wharves built for cruise ships to bring new holiday makers.

Attitudes changed quickly. Cozumel’s new islanders (the 40,000 Maya who welcomed Herman (‘Stout’) Cortes in 1519 were reduced to 30 by 1510, and Cozumel became uninhabited) realised the value, not just of their spectacular marine wealth, but also of the island’s unspoilt centre.

You’ll never get a better chance to appreciate Mayan culture so close to good beaches. The biggest Mayan site, San Gervasio (named much later), was for centuries sacred to lx Chel, the goddess of fertility, and one of the Yucatan’s most important sanctuaries. There are several others, recovered from jungle and swampy mangrove lagoons now teeming with cormorants, pelicans, primary-coloured tree frogs, iguanas and crocodiles.

These days, the duty of collective care is replacing the insensitive mistakes of the 1970s. You can see 250 species in its clear waters, including the bright blue-and-yellow queen angelfish, the toad fish (unique to Cozumel), and huge sponges like the barrel and elephant ear, which grows to 3.6 m (12 ft) across. Cozumel is fabulously pretty and exotic, and you should go there with someone you love and watch the sunsets.