Visas are not required for cruise ship passengers except those from South Africa, the People's Republic of China, Taiwan, Eastern European countries and the Commonwealth of Independent States. Take advantage of your good fortune by getting off that buffet line and out into the island. Start with some local food and a Banks beer at Millie's Snack Bar - fuel for you to 'slam tar' (i.e. walk) into nearby Bridgetown, or of course you could grab a waiting taxi. There's lots of shopping in the cruise terminal and lots to do in port, even if you only have a few hours!
For the above stated countries, visas are only needed if you will not be departing with the ship on which you arrived. Citizens of these countries may contact the Barbados Immigration Department for more information.