It really depends on what you like to do. There are water=based excursions, where you can snorkel or swim. There are shopping excursions. There are sightseeing excursions.
Bermuda has a very safe and clean bus system, and many people like to mix excursions to doing things on their own. Consider going to the aquarium, or visiting Hamilton or St. George this way.
Where will your ship be docking?