Almost everyone sees Ha Long Bay the same way: on a cruise boat. The stops below are part of the itinerary rather than places you reach on your own, so the real decision is which kind of trip to book.
A day trip leaves Ha Long in the morning and is back by late afternoon, with around six hours on the water. It covers a cave, a viewpoint and a kayaking stop, and it works if you are short on time. The drawback is that you share the bay with every other day boat, and you miss the two hours that regulars rate most: sunset and early morning, when the day boats have gone.
One night on board is the most popular choice and the one most people are happiest with. You get the same sights plus the quiet evening, dinner on deck and a sunrise over the karsts. Two nights takes you further out, into quieter water around Lan Ha or Bai Tu Long, where the scenery is just as good and the boats are far fewer.
Prices vary more than almost anything else in Vietnam, and the gap is real: cabin size, food, how many people share the boat, and whether kayaks and the guide are included. The cheapest trips usually mean a crowded boat on the busiest route. Read what is included before you compare two numbers.
Weather decides the rest. Storms between roughly July and September can cancel departures at short notice, and the port suspends sailings when a warning is in force; if that happens, operators reschedule or refund rather than sail. October to April is cooler and calmer, with October and November the clearest months. Winter mornings are often misty, which some travellers love and others find disappointing."