You probably already know this but Bermuda is far north of the Caribbean (about the same latitude as North Carolina) and has real seasons. December is firmly in the ‘winter’. That generally means temperatures are in the 60’s and low 70’s although it could be a little colder or warmer depending on weather patterns. That is going to rule out most water activities unless you wear a wet suit.
Popular attractions include St. George, the first settlement on the island dating to the 1600’s and a UNESCO World Heritage site and the Crystal Caves.
Bermuda is unusual in that visitors are not allowed to operate cars at all for safety reasons. You can take taxis, buses or, if you are a little adventurous, become proficient in moped and scooter riding. The latter sounds like the most fun option to me.
You will be going in the low-season so you will have plenty of space and nothing will be crowded. However, you will need a jacket especially if you want to ride mopeds.
Yes, I am aware of the weather. I don’t care about swimming in the ocean much, am much more interested in doing things about town. The hotel I am staying at is right on a bus line, so I should be able to get around fairly easily, and I’ve been told the ferries are good too - quicker than the bus depending on where you want to go.
In interest for others’ safety I will not be renting a scooter or moped. That’s a recipe for disaster!