It's a great island - wonderful beach, warm water, good snorkeling (not the best in the world, but very nice).
There are usually some excursions that have a charge - Banana Boat Ride, Paddleboat rental, parasailing. You can also hike (walk slowly - it's usually very hot) around the island. There's a bbq hut with great burgers, chicken, salads, etc. which is free and a bar hut that charges the same as onboard drinks.
Being the lazy person I am, I usually rent a $6.00 a day float and stay out in the water just watching the beautiful scenery. It's a thrill to see that huge ship anchored in the distance - a float is most relaxing and my idea of Paradise!