Snorkelling with whale sharks

The largest fish in the ocean is also among the gentlest. A whale shark can run to twelve metres or more, its back a slate of white spots as individual as a fingerprint, its mouth a broad slot that strains plankton from the water and takes no interest in you at all. To slip off the back of a boat and find one gliding beneath you is to have your sense of scale quietly rearranged. They gather where the water is rich. Off Ningaloo Reef in Western Australia they arrive in autumn to feed after the coral spawn; off Mexico's Isla Mujeres and Holbox they cluster in summer over blooms of fish eggs; other seasons bring them to the Maldives, the Philippines and Djibouti. A spotter aircraft or a captain reading the surface finds the animal, the boat drops you a respectful distance ahead of its path, and you swim alongside as it passes, matching its unhurried pace until it outdistances you. The encounter asks something of you. This is open water, often with swell and current, and you are finning hard to keep up with an animal that is barely trying. You need to be a confident swimmer comfortable in a mask and snorkel, and to follow the rules that keep the shark unbothered: no touching, no crowding its head, a set distance kept at all times. The ethics matter more here than almost anywhere on the list. Some sites feed captive or semi-captive sharks for a reliable show, and the animals suffer for it; a genuine encounter is with wild sharks in open sea, on their terms, with numbers in the water limited. Choose the operator on that basis, not on price or guarantee. Done well, a few minutes beside a creature this vast and this indifferent to your presence is the rare wildlife moment that only grows in memory.