We just got back from an amazing tour of Halong Bay. It is truly one of those see-before-you-die places. After searching and searching for a cruise company with good reviews, I finally found Mr.Tung with Cat Ba Ventures. Four of us rented a private sail/gunk/motor boat for three days at $110 per person. Our cook prepared simple yet delicious dishes for us for every meal, using fish caught each morning. Since it was a private boat, we were able to avoid the crowds (we only saw one other tourist boat the whole time) and take alternate routes. Lots of kayaking through caves that open up into stunning turquoise lagoons. Magical! We heard so many terrible stories about other cruise companies, so we feel very fortunate to have found Mr. Tung and Cat Ba Ventures. (Apparently another company keeps copying his reviews and posting them on their own site, so beware).