The Revillagigedo Islands, about 200 miles off the coast of Mexico, may not look like much on the surface, but beneath is one of nature's best-kept secrets: a home to some of the greatest concentrations of fish in the world. This is the only natural juncture for miles in an otherwise empty Pacific Ocean, and a crucial area for migrating sharks and other apex predators. Enter a world where whitetip sharks share living quarters with giant lobsters, humpback whales breed and thrive, and scavengers like mantas and tuna feast on plentiful bait.