Meet the dive company somewhere you can snorkel from the boat. They can meet you at or near marina cay. You can spend the day snorkeling diamond reef , wandering marina cay and scrub island.

Warren S/V Scuba Doo
Lagoon 50 (winner of best crewed yacht under 55 feet at the St. Thomas crewed yacht boat show).

https://www.cyabrochure.com/ebn/2307/pdyrX/6642/4///