We took this excursion on our November 2004 cruise. There were 5 of us: me, DH, DS11, DD8 and DD4. The beach was clean and the water was perfect! I wasn't interested in doing the stringray portion (honestly, I was a little scared of them!) But my DH, DS11 and DD8 did. We couldn't get DS out of the stringray area. He didn't even go onto the beach side.
It was plenty of time - not too much not too little. They provided lunch which was just hamburgers/hotdogs but good for a beach day. We had our own set of lounge chairs a few feet from the water. So, all in all, it was a great day.
Let me just say that in preparing for the trip, I keep telling my DD4 that I couldn't wait to swim in the ocean with her. She has never been to the beach before (we live an hour or so from the nearest Jersey beach - but I have problems with going in water when you can't see your feet!) So there was just no way we were going to the Bahamas and not going to the ocean.
Marge