This was by far our favorite excursion. We rented a car and drove ourselves. The drive is only about an hour from the hotel zone and signs have the route clearly marked. You can't get lost. It's a safe drive. There are bits and pieces of ruins throughout the park. The beaches and lagoons are spectacular. There is snorkeling, SCUBA diving, a lazy underground river, beaches, hiking, animals to see, huge turtles, pony rides, horseback riding, horse shows, dolphin shows, interactive programs, great food, and a fantastic night show. The park is very spread out so be prepared for a full day.
Be sure to bring biodegradable sunscreen because they don't allow anything else, but have no fear, they sell it here. They sell a little of everything in their gift shops. They rent lockers, snorkel gear, and towels. The lockers are on the small side though. There are freshwater showers everywhere to rinse off. There are also chairs and hammocks everywhere to relax throughout the day. No bug bites to worry about! We would definitely do it again.