One OV trip that springs to mind is Stingray City in Antigua. Despite the name there isn't a city, it's just a bar with changing facilities on a beach! Our 15 tear old boy certainly enjoyed it, as did we. The local staff were very good with helping those who were a bit nervous and also one lady who couldn't swim and was quite scared (by the end she enjoyed it so much she was the last one out of the water!) The photos they took were very good (I had it on a cd and then printed my own when I got home). It's a half day trip which leaves you time to do your own thing.
Thank you for your suggestion it has gone down very well with our son and sounds as though it is something we could all enjoy!
2 weeks to go.