Tulum is an amazing sight and is an excellent choice. I also went on an excursion to Playa Mia, which was really nice. The beach was a beautiful white sandy beach and there was a large inflatable iceberg that you could climb. Our excursion included a meal, which wasnt too bad, wasn't the best, but we still thoroughly enjoyed the beach. Also, there is a hotel called La Cieba, which is only a short taxi ride from the dock. You pay a fee to get into the hotel and you are able to use all of their facilities. If you like snorkeling, this is a great place, but the beach is full of tons of rocks. Hope some of this helps!