Which port is best for Southern Caribbean snorkeling?

We are doing a southern Caribbean cruise the beginning of Oct.

(leaving from San Juan. Going to St. Maarten, St. Kitts, Antigua, St. Lucia, and Barbados) Please Help! I trying to figure out which island is best for snorkeling? Do you go thru the ship's tour or a private? If private, any ideas as to some good ones?

Thank you for any advise you have to offer!

I just wanted to add that I wouldn't hesitate to use a private excursion on any of those islands.

It's hard to beat a catamaran in Barbados to snorkel with the turtles:) We love going with Silver Moon (private tour), and there are a couple others there that also get good reviews. If you look into Silver Moon book early and ask to get on their 12 passenger boat.

Calabaza in Barbados is also a great day, gourmet lunch & beverages included. We did turtles, shipwreck & reef & there were only 14 of us on board

Swimming with the sea turtles in Barbados was amazing. We did Calabaza a couple weeks ago and silver moon in 2004. Snorkeling at the beach between the pitons on st Lucia was amazing.