Manuel Antonio is the smallest national park in Costa Rica, and the sea put it together. Punta Catedral, the forested headland at its centre, used to be an island. Currents sweeping past dropped their sand in its shelter until a neck of it grew all the way back to the mainland, and that neck is what you walk out on, with a beach on either side of you. Espadilla Sur lies on one; in the crook of the point lies Playa Manuel Antonio, the calmest, shallowest water in the park, bath-warm and ringed by trees. A trail then rings the old island, seventy-two metres of it under forest, breaking out at lookouts where the canopy stops at a cliff and the coastline curves away in both directions. You can walk the whole of it in a morning.
The animals are what fill that morning. Three of Costa Rica's four monkey species live in the trees over the sand. Howlers start roaring before dawn, capuchins come down to the beach and long ago worked out what a rucksack is, and squirrel monkeys, the rarest residents here, stream overhead in fast chattering troops. Their Pacific population has fallen to a few thousand animals, holding on almost entirely in this park and the forest corridors near it. Two kinds of sloth hang in the same canopy, the brown-throated three-toed and Hoffmann's two-toed, both so slow and so moss-tinged that they are the thing everyone misses. The guides at the gate carry scopes and pick out what you would walk straight underneath. Toucans and fiery-billed aracaris cross the high branches, their outsized bills flashing against the green. The park shuts in the afternoon, so the end of the day belongs to the beaches just outside it, which face due west. The sun drops into the Pacific from there and the water turns copper as the heat finally lets go.