If you do this trip again i made an awesome mini-adventure you can add to your schedule - a real-life treasure hunt near Ha Long Bay.

While I was visiting Cat Ba Island (by Ha Long Bay), I hid a coin in a really awesome location, then took photos to use as clues to find it. I wrote a blog post with details here: https://mytefl.net/blog/i-made-a-real-life-treasu...

You'll need to stay overnight on the island, and would have to spend an afternoon looking for the clues and hiking up to the finishing spot. P.S if you do get there, please take a photo and let me know!