Well, ABANKS isn't exactly free, just the snorkeling right there at the shop is. The site is Eden Rock. You can rent tanks, weights, all the rest of the gear and scuba there too, if you remember your C-card.
I went with <a href=http://www.neptunesdivers.com/index.html>neptunes divers </a> I have no difficulty recommending them. They will accommodate a cruise divers schedule and they won't charge you if your ship can't tender passengers ashore.