Swimming with whale sharks in Cancun: An underwater safari

About 25 miles off Cancun's northeastern coast, past Isla Mujeres and far into the Caribbean waters, some of the largest known sea creatures loll their summers away. They are whale sharks, a gray-and-white spotted fish that can measure up to 40 feet long and weigh more than 15 tons. That's bigger than many dinosaurs.

On this particular late August morning, I would be hanging out with them for a while. Hopefully, they'd already eaten breakfast.