The Peten branch of Guatemala's Wildlife Rescue and Conservation Association sits on the north shore of Lake Peten Itza, accessible by boat from Flores. ARCAS receives spider monkeys, parrots, macaws, jaguars, and other animals confiscated from the wildlife trade and rehabilitates them for release back into the surrounding jungle.
The site has a small visitor area with rescue animals that cannot be released — it is not a zoo, and only a fraction of the rehabilitation is on view — but the work is genuinely important and the boat trip across the lake is a pleasant half-day in itself. Combine with a swim and lunch on the north shore.