The absolute best excursion by far is to Saona Island. You go by boat with a tour guide and there is a lunch set up on the beach, you spend the afternoon swimming, dancing, and relaxing. This is a full day excursion, if you are staying at a resort you can inquire there, and if not you can just call the Dominican tourist board and they have all the info. The Island is absolutely the closest thing I've ever seen to paradise.
I cannot remember the price, but it is well worth it!!!
