From Tuan Chau Pier there are two main boat day trips of Halong Bay. Route One (100,000d, four hours) potters around the waters of nearby islands, visiting the caves of Hang Dau Go and Hang Thien Cung. Route Two (150,000d, six hours) heads further into the bay to Hang Sung Sot and Dao Titop.
On these trips you also have to factor in the separate admission costs to the national park and to each attraction. These day-trip tours are an entirely local tourist experience. Expect a packed boat and boisterous Vietnamese karaoke tunes pumping from the stereo as your soundtrack.
If there's a group of you to share costs, there's the option of hiring a complete boat and creating your own itinerary (per hour Monday to Friday 400,000d, per hour Saturday and Sunday 500,000d).
These boat day trip prices are officially regulated.