Cat Ba is quite small and very quiet in the off season. It looks as though it becomes incredibly busy in the Summer. We found Mr. victor Thang (pronounced Tang) who helped us with day tours on the Bay, motorbike rental, maps, good tips and travel back to Hanoi via Haiphong. (if you prefer the train to the bus, as I do, go via Haiphong)
Here are his contact details, should you need a hand. He is generous, has good English, and looks after you with kindness.
0974 779 870
You do not need to be staying at the Thai Bao Hotel to engage his assistance.
Enjoy Cat Ba!