anyone have some good recs for private excursions for Eastern Caribbean (Nassua, St. Thomas, St. Martin) for snorkle, scuba, and/or beach trips?

You might want to check out our sister site PortReviews.com. All three of those ports have been researched throughly and not only do the editors make suggestions, but you will also find a number of reviews by other cruisers who have specific suggestions for activties, beaches, etc at each. Here is the link to the page. Once there just click on the hyperlink in the left column to be rediredcted to the specific port:

http://www.caribbeanportreviews.com/#Eastern

Hope the info helps.
Nancy