In Freeport, we took a taxi to the beach, which cost $14/person return. We were going to go to the marketplace and the beach at Great Lucayana, but our driver convinced us to go to Junkanoo, aka Taino, Beach. We had a good time, but it was not the greatest beach. Lots of garbage, rocks, and pushy people. I really wish we'd have stuck with our plan.
In Nassau, we booked our own excursion with Stuart's Cove. I'd found them on Trip Advisor. I did not have to prepay. They picked us up an hour and fifteen minutes after we arrived, at 12:15, right near the ship, and dropped us off two hours before departure at 6pm in the same spot. We snorkelled at two different reefs, which were amazing, and then went to a third spot to snorkel with reef sharks. That was something I will never forget! The excursion cost $258 total for the four of us, which was way cheaper than most Carnival excursions would cost, so I highly recommend them.