The Playa del Carmen coast

Offshore of Playa del Carmen runs the northern end of the Mesoamerican Barrier Reef, the second largest reef system in the world after the Great Barrier Reef. The Yucatán Current sweeps north along it hard enough that almost every dive along it is a drift — divers go in, and the boat follows their bubbles.

Between November and March the same stretch hosts something unusual: female bull sharks come in to the 25–30 m sand flats off Playa to spend the winter, and the town has built a seasonal shark-diving industry around them. Whether or not they are fed is a live argument locally.