Las Baulas National Marine Park protects 445 hectares of Pacific coastline where leatherback turtles — *Dermochelys coriacea* — have nested for millennia, their arrival window stretching from October through March when warmer currents bring plankton blooms offshore. The park was established in 1991 after biologists documented catastrophic declines across the eastern Pacific population, with nesting females dropping from an estimated 1,500 in the late 1980s to fewer than 100 by the early 2000s. Playa Grande, the park's anchor beach, remains one of the last significant leatherback rookeries in the Americas, though numbers continue to fluctuate with El Niño cycles and illegal take in distant foraging grounds. Leatherbacks are the largest living turtles, averaging 400 kilograms and measuring two meters in carapace length, and their nesting ritual follows a pattern older than the isthmus itself. Females haul themselves above the high-tide line, excavate a flask-shaped chamber with their hind flippers, deposit 80 to 100 soft-shelled eggs, then camouflage the site before returning to the surf. The entire process spans two hours. Peak nesting occurs between midnight and 3:00 AM, though early arrivals begin around sunset. Artificial light from coastal development has historically disoriented hatchlings, prompting strict dark-sky ordinances across the buffer zone; Tamarindo's beachfront now operates under red-filtered lighting during nesting months. Turtle nesting Tamarindo tours operate under mandatory guide protocols enforced by park rangers, with group sizes capped at fifteen and approach distances regulated to minimize disturbance. Guides monitor radio frequencies linked to patrol units stationed along the seven-kilometer beach; when a nesting female is confirmed beyond the vulnerable crawl phase, groups are escorted to observation points. No flash photography is permitted, and red-lens headlamps are distributed at the trailhead. The park entrance fee — twelve dollars per visitor — funds beach patrols, hatchery operations, and community education programs that have reduced poaching incidents by 90 percent since 2010. Conservation outcomes hinge on international cooperation; leatherbacks tagged at Playa Grande have been tracked foraging off the coasts of Chile, Peru, and the Galápagos, underscoring the migratory distances these animals traverse. The park's research station maintains a photo-identification database spanning three decades, allowing scientists to track individual females across nesting seasons and correlate reproductive success with ocean temperature anomalies. Volunteer programs recruit seasonal monitors who patrol nightly, recording clutch counts and tagging new arrivals, work that has generated peer-reviewed data cited in IUCN assessments and regional management plans.