Looking for Swimming with Turtles in the Bahamas Tour

I’m cruising in March from NYC to the Bahamas. I’m looking for the best excursions to swim with turtles. We’ll be stopping at Nassau, Great Stirrup Cay, and Port Canaveral. From my research it appears the most likely place to be able to snorkel with the turtles is at Green Turtle Cay, however it doesn’t appear that NCL has a tour there. Does anyone have any recs of outside excursions etc. or snorkeling with turtles? Thanks!!!