Taking to the Halong waters is, in its essence, a way of putting yourself right in the action. Many of the tour operators will carry snorkeling or kayaking equipment onboard the vessel, which you can rent out. Halong Bay and the surrounding region has very rich marine life (dolphins, seals, coral, and hundreds of species of fish), so grabbing a snorkel mask and some fins is the best way to check it out. Expert tip: The Bai Tu Long Bay area falls under the protection of the National Park, so the waters and marine life here are even better.
Some of the most exquisite parts of Halong Bay are the secluded beaches and caves, which are very often not accessible in the larger cruise vessels. Taking out a kayak will give you the chance not only to explore the area at your own speed, but you may also get to experience a part of Halong Bay that few others have seen.