ok y guess is you are on Carnival Victory

I have been on those islands two times, I cruised three times on carnival Destiny plus I am from Puero Rico so any question feel free to ask.
As I remember there are no option for a day at the beach near or walking distance from port because, on most ports, they need it to be deep in order to fit the cruise ship on port. I guess there is only one and is on Barbados but I will recomend you to get a tour to be sure to get the best beach for your time. Remember is your cruise if you really are going to experience the caribbean get the best available...