Every year in July, the waters around Isla Mujeres, just off the northeastern tip of the Yucatán Peninsula, become the stage for one of the largest gatherings of whale sharks. These creatures, the world’s largest fish but harmless to man, congregate to feast on vast slicks of tunny eggs and are joined by bottlenose dolphins, manta rays, marlin and sailfish. The Blue Sphere Foundation offers the opportunity to freedive with them, accompanied by the Emmy-award-winning cinematographer Shawn Heinrichs and National Geographic’s Paul Nicklen and Cristina Mittermeier, who will film and take still pictures of the dive. Heinrichs is a powerful voice in the campaign to reduce shark fishing – 100 million are killed worldwide for their fins each year – and is retraining local shark fishermen as tour guides. The trip, from July 13 to 17, costs $15,000pp based on two people, with 50 per cent of proceeds going to the Blue Sphere Foundation’s conservation projects.