Las Baulas National Marine Park protects 445 square kilometers of Pacific coastline, mangrove estuary, and open ocean where leatherback sea turtles—the world's largest marine reptile, reaching 700 kilograms—return each year to nest on Playa Grande's dark sand. Established in 1991 to safeguard critical nesting habitat, the park extends three nautical miles offshore, encompassing coral formations, volcanic rock reefs, and seasonal aggregations of manta rays, spotted eagle rays, and bottlenose dolphins that follow the Papagayo winds south from the Gulf of Papagayo each winter. Tamarindo catamaran snorkel tours depart from the river mouth where the Matapalo Estuary meets Tamarindo Bay, a sheltered launch point that shields vessels from the swells generated by the Nicoya Peninsula's exposed western shore. The catamaran's twin-hull design—developed for stability in open water—allows captains to anchor within 30 meters of coral outcrops without damaging the substrate, a requirement enforced by park rangers who patrol the Las Baulas marine corridor daily. Most sailings follow a northwest bearing toward Playa Conchal's white-shell beach or a southern route to Punta Guachipelín, where underwater visibility averages 15 meters during the December-to-April dry season and volcanic boulders create surge channels that funnel nutrient-rich currents past brain coral colonies and gorgonian sea fans. Snorkeling sites within the park's boundaries hold populations of king angelfish, Moorish idols, and Pacific green sea turtles that graze on algae beds between deeper foraging dives. Olive ridley turtles, smaller than their leatherback relatives, surface near the catamarans during morning departures, their carapaces worn smooth by decades in open ocean. The park's western boundary intersects the Costa Rica Thermal Dome, a seasonal upwelling zone that draws hammerhead sharks, sailfish, and humpback whales into waters less than 40 meters deep, visible from the catamaran deck between July and October when nutrient concentrations peak. Tamarindo catamaran snorkel tour operators coordinate launches with the park's tidal schedule, departing two hours before high tide to ensure calm conditions over the reefs and safe passage through the estuary's sandbar. The marine park's 12-dollar conservation fee, collected at entry points along Playa Grande, funds ranger patrols, turtle monitoring stations, and mooring buoys that prevent anchor damage to coral—infrastructure that has kept reef degradation below 8 percent since 2018, according to annual assessments by Costa Rica's National System of Conservation Areas.