Cahuita National Park protects the largest living coral reef on Costa Rica's Caribbean coast, a 240-hectare underwater plateau that extends nearly two kilometers offshore from Punta Cahuita. Established in 1970 to halt dynamite fishing and anchor damage, the park now shelters 35 coral species, including elkhorn, brain, and lettuce formations that thrive in the warm, low-turbidity waters fed by the confluence of the Perezoso and Carbón rivers. The reef supports over 120 fish species, from queen angelfish and blue tangs to spotted eagle rays that patrol the sandy channels between coral heads. Green sea turtles and hawksbills nest on the park's nine kilometers of undeveloped beach, and sightings in the shallow reef zones are common year-round. The Puerto Vargas sector, accessed via a paved entrance three kilometers south of Cahuita village, serves as the primary gateway for snorkeling excursions. The reef system here begins just 20 meters from shore, where depths range from one to eight meters, allowing snorkelers to drift above staghorn thickets and observe parrotfish grazing on algae-covered coral. Visibility averages 10 to 15 meters during the drier months of February through April and again from September through October, though the Caribbean's year-round warmth—water temperatures holding steady near 27°C—makes Cahuita one of the few Costa Rican snorkeling destinations with no true off-season. Unlike the Pacific's rocky volcanic shores, Cahuita's coastline is a legacy of ancient reef-building: the park's coastal trail follows a raised fossil reef terrace, its limestone foundation laid down thousands of years before the present reef began growing. This geologic continuity gives the landscape a rare horizontal calm, with white sand beaches backed by coconut palms and sea grape rather than the steep rainforest descents found elsewhere in Limón Province. The result is a hybrid ecosystem where lowland tropical forest meets Caribbean reef, and where howler monkeys call from cecropia trees within earshot of breaking waves. Snorkeling Cahuita tours typically pair reef time with a guided walk along the coastal trail, where sloths, white-faced capuchins, and green iguanas are frequently encountered. The park's dual-access model—a fixed entrance fee at Puerto Vargas and a donation-based entry at the Kelly Creek ranger station—reflects its community origins, and most guided tours enter through Puerto Vargas to guarantee reef access regardless of wave conditions. The shallow, sheltered bays here allow even novice snorkelers to observe the reef's architecture: coral polyps extending their feeding tentacles in daylight, cleaner shrimp stations attended by yellowtail damselfish, and the occasional southern stingray buried in sand with only its eyes exposed.