You will probably have time to make it, but it will be tight. We also found the place to pick up the tour difficult to find.
We enjoyed the day, but many of the above comments are also true. The snorkeling was not good at all; unfortunately true for most places in the Caribbean now. The seas was not rough the day we were there. Murky water at the wreck and other site and little sea life to see.
The meal was ok, I enjoyed the rope swinging myself, both watching and doing, and didn't notice it rocking the boat, but I don't normally get sea sick.
The worst thing about the tour was that the dancing got extremely raunchy--there were children on the boat and It made me uncomfortable. Also very loud music. Would we do it again? Maybe.