It was cancelled about an hour after we arrived so I only saw it from the ship but we've been there before and it's a great day for lounging at the beach!
We just took the boat to the main town and did some shopping. It was convenient but very hot. Hagglers in the shops weren't too bad.
Take a cab (not the ship excursion) to Sapphire Beach. It was just 10 dollars per person each way and the lounge chairs are just 7 per person. In total it comes to about half of the ship price. A great day!