Hi Flint, your cruise is coming really soon! Barbados is a tad away from a beach. The cab drivers there took us for a lot of money, $85/pp. However, he did drop us at a great beach. It was a little down from the Folkstone Underwater Marine Park, great snorkeling, lots of places to get local flying fish sandwiches and beverages. We rented chairs and an umbrella for $10 or something reasonable. I have read on this board that you can take the local bus, but I don't know how to do that. The cab driver did come back as promised, and we did have a wonderful time.
If you like spicy sauces, try the bajan pepper sauce there. I always buy a couple of bottles to bring back. It's hot, but really tasty. The base is mustard and mango with a ton of scotch bonnets, but so very good. I've actually made some at home, not as good as the ones from Barbados, but good just the same. There's a shopping area at the pier and it's reasonably priced.
Here's wishing you calm seas, perfect weather, great food, and a marvelous cruise!