Playa Grande is a very important nesting beach for the leatherback turtle (Baula is the Spanish name for this species). This is the world's largest and most wide-ranging sea turtle, nesting in beaches from Surinam to Malaysia and some individuals have been found as far north as Iceland and Scandinavia. Leatherbacks arrive at Tamarindo in early October and nest until March, with the peak of activity occurring during November and December.

Pottery has been found at the archeological sites of Matapalo and Herta Aguacate, adjacent to the park. The artifacts found are mainly bowls of different sizes that are decorated with blackish coffee colored engobe, and complicated geometrical designs.