The Cozumel Reefs National Marine Park protects 11,987 hectares of the Mesoamerican Barrier Reef System, the second-longest coral barrier in the world after Australia's Great Barrier Reef. Established as a federal reserve in 1996, the park extends along 32 kilometers of Cozumel's western and southern coastline, encompassing three distinct reef formations—Palancar, Colombia, and Paradise—each dropping from shallow coral gardens at five meters to dramatic walls exceeding 40 meters. The conservation fee of 225 MXN per person, per day funds reef monitoring stations operated by CONANP, Mexico's National Commission of Protected Natural Areas, and supports the park's turtle nesting programs. Paranormal visibility averages 30 to 50 meters year-round, a function of the Yucatán Current that sweeps north from the Caribbean Basin at speeds reaching two knots. This same current delivers nutrient-rich water that sustains over 500 documented fish species, 65 stony coral species, and resident populations of loggerhead and hawksbill sea turtles. Palancar Reef alone spans seven kilometers and features swim-through caverns carved by millennia of wave action into the fossilized coral platform. Colombia Reef, the park's southernmost formation, hosts cleaning stations where green moray eels and Nassau groupers queue for service from cleaner wrasse and pederson shrimp. Snorkeling Cozumel tour operators launch from the Southern Coastal Highway between kilometer six and Punta Chiqueros, the park's designated access corridor. The 06:00 to 22:00 operational window accommodates tidal variations, though the morning arrival window between 06:00 and 10:00 delivers optimal conditions—easterly trade winds remain calm until late morning, and cruise ship tenders do not reach the reef zones until after 11:00. Water temperature holds steady at 26 to 28 degrees Celsius, requiring only a rash guard for thermal protection. The park prohibits sunscreen containing oxybenzone and octinoxate, compounds proven to trigger coral bleaching at concentrations as low as 62 parts per trillion. Cozumel's reef system records date to Spanish chronicler Juan Díaz, who accompanied Juan de Grijalva's 1518 expedition and noted "waters so clear one could count stones on the bottom at ten fathoms." That clarity persists today, maintained by the island's lack of river discharge and the reef's position in the open Caribbean, far from sediment plumes that cloud continental coastlines.