It's been YEARS, but a guy named Austin had an outfit called Pro Divers. They were the ones that came out to the cruise ship when the wife and I passed thru the St. Kitts/Nevis area on a Windjammer cruise.
I'd have to say the diving was rather casual....we just did one day, two-tanks, and did not have cameras (or our own gear) at that time. I have fond memories of it, but this was just after getting certified and before I'd really dove anywhere else notable at all. I don't think the depths or currents were terribly challenging, so a seasoned diver could probably make a lot more out of the dives than we did at the time.
Do a search and you'll find a couple other postings about ProDivers, Austin, and other operators I suspect. I think I've seen them, if not here then back when I used to post on Scubaboard.
Enjoy your trip!
rtrski