Mason’s life-changing moment can be traced back some 7,000 to 10,000 years. That’s when scientists estimate Sweetings Pond filled with ocean water that filtered in from nearby Hatchet Bay (roughly one mile east) through underground cracks and holes. The landlocked saltwater lagoon, in turn, became a fortress for brittle stars, spider crabs, octopuses, bioluminescent plankton, and, of course, the seahorses. A refuge where several of the species’ regular predators—skates and rays, tuna, sharks—can’t possibly break in. “It’s an island on an island,” explains Mason.