The premier snorkelling experience in Bonito: float 2 km downstream in gin-clear water watching piraputanga, dourado, pacu, and dozens of other fish species moving around you as if you were inside an aquarium. The forest canopy overhangs the river and the current does most of the work. Wetsuits are provided — the water is cool. Book through a local agency; the reserve limits daily visitor numbers, so availability goes fast in high season.