This is listed as a 6 hour excursion, with a 25 minute bus ride to get there. Do you have to stay there the whole 6 hours or does the bus go back to the port/ship every couple of hours? This sounds like fun but 6 hours at the beach is way too much son for me.
We did this excursion a couple years back, and I think you have to take a taxi back if you leave early but I can't remember for certain. We stayed the entire time because they keep you busy the entire time. Games both on the beach and in the bar/restaurant area: lunch, beer drinking contest. tug of war, dance contest, egg toss, etc. The time went by really quickly.