Swimming with whale sharks big tourist draw
As many as 1,400 whale sharks, the world's largest species of fish, migrate through Cancun's warm coastal waters between mid-May to mid-September each year to feed on plankton in the Yucatan Peninsula.
Tourists with snorkeling gear take turns swimming alongside the gentle giants, which can reach up to 50 feet in length but pose no danger to humans.
"Swimming with the biggest fish in the world is certainly something unique. They won't hurt you. They're on their own business, just feeding themselves," said Kenneth Johnson, a marine biologist whose company, EcoColors, runs eco-adventure excursions in Mexico.