We originally wanted to do a day trip to Halong Bay to maximize our stay in Hanoi and but found it easier to do a 2day/1night excursion and catch a flight to Siem Reap the next day after the Emeraude cruise.
Here is a reply from “bearsy1" to my post " Trip to Vietnam October 2007".
Hope this helps.
" Posted on: 12:38 am, February 01, 2007 Save
hi there fellow a-towner!
we booked our halong bay trip when we got to hanoi with our hotel. the tours are kind of madness. we stayed in the old quarter and there are travel agents no kidding about every 50 meters, most of them within hotels. ours cost about US$25 and we didnt stay the night, we just went for the day. i honestly dont think it would be worth going on one overnight. the tour arrangement was not as i had expected, and not what tours in australia are like. you book with your agent and they arrange for the bus to pick you up. when the bus picks you up, there are people who are staying overnight, going for 2 nights, or going for the day. when you reach halong city, the bus driver kind of gives you to someone who runs what tour you were after. they take you out for the day, then when you get back, they direct you to a bus to take home. so you dont end up staying with the same group of people or tour guide all day. also, there are hidden costs. we had to pay $2 to go out on a little dingy boat through caves. also if you want seafood with lunch, they take you to floating houses to buy it from. just little things like that. concerning seasickness, you would probably be ok on the day trip. you dont spend the whole time on the boat - you get off to look through caves. they are also pretty steady boats. i would suggest you go to the doctor and get a little gem called stemetel before you go - its for nausea. my brother gets intense motion sickness and takes it and it works wonders. the trip to and from halong bay was fine. all agents will put you on a fairly new ford minibus - similar to a des's mini bus type thing - to and from halong city. it takes about 2 hours and you have a break at a large shop that employs disabled children. the bus was airconditioned, in excellent condition, and the tour guide we had on the bus gave a funny little intro for the first 15 minutes. "