We've done a lot of tours with Viator in Australia, Greece.....and other countries and we never had any trouble at all. This time, the trip to Halong Bay was amazing! The pick-up was on time and the crew was waiting for us at the port according to the schedule. Crew service was very good, they were attentive and willing to help us at any moment. Food was delicious!! The limestone cave was very interesting but we thought our boat guide was going to stay with us during the visit and he didn't, so we were not able to ask any questions and help ourselves at the cave. The summit we visited next day was interesting too and we had a beautiful view of the bay. I think we should be allowed to guided-tours to lagoons and other interesting places in the kayaks because we didn't know the place and we try to be as close as we could to the boat . Tour Guides should also give tourists a short introduction about Halong Bay before we start the tour (animals, number of islands, plants.........). Eventhough the cabin was clean, I found two cockroaches!!!!! Overall, we had a great time, experiencing the beauty and the peace of this "wonder of the world". We recommend a two-day tour.