Isla Mujeres is one of the best places to swim with whale sharks in Mexico because of the plankton-rich ocean waters surrounding the island. Between June and September is the best time to go. During these months sharks in the hundreds congregate north of the island, where the Caribbean and Gulf of Mexico converge, to feed on plankton. Other times of year most sharks are seen swimming solo or with one or two other sharks. Myriad tours are available including diving expeditions and boat tours. Lesser known Isla Holbox, a tiny island oasis a short boat ride from Cancun, is another excellent choice for whale shark diving. The industry is managed by the World Wildlife Fund who teams with local guides to provide a sustainable experience ensuring no ill-effects from the tourist industry. more