Snorkeling Australia’s Great Barrier Reef brought me face-to-face with giant clams, colorful coral gardens, clownfish, and a famously friendly Māori wrasse.Manta rays swimming through the Great Barrier Reef.Credit: Colin Baker/Getty ImagesAs the submarine slipped beneath the surface, the bright Florida sunshine disappeared, leaving only the eerie blue glow of the searchlight and a flurry of bubbles that obscured the water outside my porthole. On…