You can also do a day tour of the ruins of Nim Li Punit and Lubantun. Monkey River Town is still there; it makes for a pleasant, but short walk after the meal that comes with the day trip. I only regret that I did not slip into the local bar to get a quick feel for it.

For snorkling, Ocean Motion near the lower end of the sidewalk is good and a bit less expensive unless you use a credit card.