We did the glass-bottom boat tour of the Bermuda triangle at night. It was a lot of fun. We had a great captain/tour guide and it was truly amazing. Yours would be even better, as the water is warmer and the more colorful fish are around. You could book it at the pier, but it was only 5 dollars more to book on the ship.And because we had booked an excursion, we were able to buy our bus passes from guest services and didn't have to wait in the line getting off the ship.
Just make sure you bring rain gear. As beautiful as Bermuda is, they have an average of 180 days of rain, and it is usually windy!