In addition to colorful coral reefs and magnificent beaches, Mexico's Riviera Maya offers unique underwater adventures. North of Isla Mujeres, snorkelers swim with whale sharks and manta rays while divers plunge beneath swirling schools of baitfish corralled by circling sailfish. Big thrills continue when bull sharks congregate off Playa del Carmen each winter. Very different adventures await those who immerse in the clear fresh waters of the cenote caverns that riddle the coastal landscape. Also in the mix are easy boat rides to spur-and-groove reef formations, shipwrecks, the world's largest underwater sculpture park, and day trips to the reefs of Cozumel. Ashore are ancient Mayan cities and a world-class vacation destination.