The world’s largest aggregations of whale sharks (the largest fish) are in the Caribbean off of Isla Mujeres, Quintana Roo, Mexico. The season for swimming with them is May 15-Sept. 15, with best sightings late July through August.
On trips of five to six hours offered by Ceviche Tours (Isla Mujeres, Quintana Roo; phone [044] 998 135 4787… and in New York, NY, at 631/470-6315), up to 10 guests cruise for eight to 25 miles to find whale sharks, then swim with them or take photos from the boat.
$125 per person includes licensed diver-guides and lunch. Snorkel gear and flotation devices provided.
The fourth annual Whale Shark Festival, July 15-17, 2011, in Isla Mujeres (near Cancun), offers food, music, dance troupes, educational booths (tour the turtle farm and nearby preserves) and seminars on marine conservation. Free entry.