The Cayos are very flat so no waterfalls. Inland its mostly scrub but the beaches are very good. The Jungle Tour is based on Guillermo its self drive speedboats round the Mangrove lagoons,great fun you also get to snorkel. The catamaran trip is also good. We also got a taxi to Playa Pillar which was a favourite of Hemingway there is a beach bar there but it is otherwise undeveloped great if you love beaches.
There was also the little red bus that tours all the resort hotels on Guillermo and Cayo Coco you can get on and off at your leisure.