We did this in December and really enjoyed it. Air conditioned coach drove us through the city to a private marina, pointing out highlights and telling us of the history of the Island along the way. At the marina we boarded a pontoon boat. The ride was gentle and informative as we learned about the area, the homes, and the effects of prior hurricanes (including the high water mark of the last severe one) and the mitigation efforts to protect property and people form future ones. Then to the mangrove forest, where we were taught about its biology, its protective aspects, its life cycle. We got to handle some of the plant. If we wished, we got to safely handle a jellyfish. On the way back to the marina we learned about an invasive iguana species, and had them pointed out [after which you noticed them everywhere...]. Once back on land the coach took us for more of a drive, and a stop at "Hell" (an overlook over a geological formation, which also has a little store). We stopped at a nice public beach that is right beside IIRC the Governor General's residence. That was about a half-hour stop -- there was shade near the parking area if one wanted to stay out of the sun. Then back on the coach and deposited back at the port. Enjoyable, relaxing, educational. Bring sunscreen and/or sun protective clothing, sunglasses, and a wide brimmed hat.
SW