The main attraction of the park starts in July and lasts until December when hundreds of Olive Ridley Sea Turtles assemble off the coast then barrage the beachhead during the nights that precede a full moon. These mass beach arrivals that occur every three or four weeks are known locally as arribadas. Each arribada lasts about a week, as wave after wave of turtles swim ashore, sometimes totaling up to 150,000. The Ridley can be sighted making its way inland at all times of the year-though far less frequently after the typical mating season. Leatherbacks and Pacific green turtles can also be sighted from October to January.

Residents of Ostional have collaborated with state officials to organize an imaginative conservation effort that benefits both the Ridley and the local economy. The number of turtles during the Ridley's arribadas can be so great that eggs laid on the first few nights are frequently destroyed by the next wave of turtles storming the beach. Thus, the locals are allowed to harvest the first clutches of eggs and sell them at a fair market price. This sanctioned cultivation has actually resulted in the hatching of more eggs, while simultaneously weakening the black-market for plundered eggs.

Aside from the turtles, many other animal species make the national refuge home including iguanas, monkeys, coatis, crabs, and many birds. The south end of the refuge near the Nosara River is home to many estuaries and mangroves rich in neotropical fauna.

Nearby Tamarindo offers park visitors convenient accommodations.

The bus ride from Nicoya lasts about 2.5 hours if road conditions are good-expect delays if roads are in disrepair. Private bus tours also run from San Jose. Flights from San Jose and Liberia run daily to Nosara, and are usually quite economical.