We took a short tour of Nassau and Atlantis and then we went to a public beach close to the port. We took a taxi. We enjoyed our day and it was a reasonable price!
The excursion was in the afternoon (we docked at 2 p.m.) and we reached the beach when the sun was already down. We enojoyed the falls although it was quite a "strong" experience, but we recommend to do this excursion only if you have all day and not only one afternoon!
We took a taxi at the port and reached West Bay beach indipendently, it is a nice beach, but be aware that there are a lot of people at the beach offering all kind of services, they might be a bit annoying. Roatan is quite a poor place, driving from the port and passing through the "main town" it can be quite touching to see how most of the people live. Our ship offered an excursion to "Tabyana beach" which is a part of West Bay, but I would recommend to take a taxi and stop in a less crowded area of the beach (if you are looking for a relaxing experience, if you are looking for fun, then Tabyana is OK!)
We took the public boat to Caye Caulker, it is a 50 minutes trip to a wonderful place in the middle of the sea! Belize does not offer beaches, so be aware that there is a lot of snorkeling to do, nice food, wonderful nature, but not white long beaches! We enjoyed our excursion quite a lot, anyway!
We went to Tulum ruins and then Xel-Ha water park. It was fun!! Our guide was super professional and nice, she explained a lot about the culture and history of the places, really gave us a wonderful explanation. Xel Ha is basically an "aquarium" where it is possible to swim with the fishes and do a lot of activities. The food is super good and all included!! We recommend it!