Volcanic islands, such as San Benedicto, are part of a 25,000-mile volcanic chain that runs around the Pacific Ocean. It's known as the Ring of Fire.
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.
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