//
Organised 2- or 3-day trips into Ha Long and Bai Tu Long Bay for kayaking, caving, swimming and diving. Book via the honest and fair Mr. Lu at the post office. Prices ~US$45 per person for 2-day, 1-night trip (assuming 4 people in group).
The domain of the endangered Cat Ba Langur, of which there are supposed to be only around 100 left. Things on offer include a walk to a peak viewing tower (1½-2 hr round trip; slippery and muddy if it's rained recently), a frog pond (probably better in the off (wet) season), a short nature walk near the frog pond, more stuff which you can probably find online.