We visited Halong Bay for a 2 day 1 night cruise last year and to be honest I found it the worst ever excursion that I have been to. Ok, the nature is gorgous, but that it all. All boats went the same way for the same stops. I felt that nothing was authentic, even the local floating village that we visited felt like set up for tourists like noone actually lived there. We checked a lot of different options (all looked the same in terms of itinerary/food etc.) and went with Emperor cruise which was recommended by the concierge at the Metropole hotel in Hanoi. Small boats with only 8 cabins (all large suites), so it should be rather exclusive, also reflected in the rates paid. We were upgraded to their best suite (royal suite - 70 sq meters), but hardly had any time to enjoy this suite at all since the cruise was packed with all kinds of activities of which they should have left out most to to allow for time to just enjoy. Even the "free" massage (included) felt like so rushed in between everything that we did not book time for it. The whole experience felt so over-planned and "plastic" with the team on board saying the same things and waving at us every time we left and came back. They seemed afraid of removing any activity from the schedule since all boats offer the same things and noone wants to do less. For example squid fishing was done after dinner. We have done that before and thought it was fun, but there was just no squid at all and one of the personnel even admitted that no tourist had been able to catch one for almost a year!!! Food was plentyful and inclued luxury items like lobster etc., but felt mass produced. We really regretted going on this trip and I strongly suggest that you do not go. And about Halong Bay mainland; An over developed place where Chinese investors have taken over, totally ruining any local charme which was there before.

Sorry for being so negative, but I am really just trying to help you not making the same mistake as we did.