The Ha Long Bay cruise guide, from the data

Almost everything written about a Ha Long cruise is written to sell one. We came at it the other way. We tracked seventy overnight boats, recorded what they publish and what they hide, and read 7,104 guest reviews about them. This page is the short version of what that turned up, laid out as the decisions you have to make in roughly the order you make them. Each section points to the fuller guide behind it.

First, which bay

The name Ha Long now covers three bays, and where the fleet sails has shifted. Of the seventy boats, thirty-six sail Lan Ha, twenty-three sail Ha Long proper, and eleven sail Bai Tu Long. Lan Ha is the default now rather than the alternative, and Bai Tu Long is the quiet one: fewer boats, fewer of them in your photographs. The three are close together and genuinely different on the water, and the choice matters more than the marketing lets on. Our guide to the three bays sets out what each one trades away.

Then, the boat

Two things you would expect to separate the boats do not. Kayaks are on sixty-nine of the seventy, and a jacuzzi on sixty-two, so choosing a boat on either is choosing on something that barely varies. What does vary is size and age. The fleet runs from four cabins to fifty-six, and the price hardly moves across that range, which makes how many other people share your boat one of the few things you can pick without paying for it. Age is murkier: the boats span 2007 to this year, but the number that would actually tell you about condition, the last refit date, is published by none of the seventy.

How long, and where you leave from

Every boat sells both a two-day one-night and a three-day two-night trip. We cannot compare the two prices for you, because only one boat of seventy publishes a three-day rate, so the choice between them comes down to time rather than money. The harbour is quieter and more useful than it looks: forty-two boats name one, all on the Ha Long City side, and every boat that leaves from Hon Gai sails to Bai Tu Long. Our guide to which harbour you leave from turns that into a shortcut, and the one to Cat Ba and Ha Long City covers where your spare hours go.

What it costs, and what it does not

The advertised price is designed to look small. Across the fleet it runs from $80 to $615 a person, but that is a per-person floor, and on some boats it is a cabin rate quietly halved, so the real bill can run several times higher. Our guide to what a cruise costs untangles the two price bases. The fare is also narrower than it looks: only three of 139 listings include the Hanoi transfer, the single biggest cost most people forget, which is why what is not included matters as much as the headline rate. And the cancellation terms vary more than anything else on the market, with seven different penalty ladders and no standard among them.

What the reviews actually reveal

Here is the finding that surprised us most. Food is the single most discussed subject on board, and it tells you almost nothing: guests raise it just as often after a bad trip as after a good one. What separates a one star trip from a five star one is quieter and invisible in a photograph. A cut itinerary appears in 28% of angry reviews and 1% of happy ones. Surprise charges and booking trouble follow the same pattern. Our guide to what guests complain about lays out all of it, and the companion guide to life on board shows the same truth from the other side: the thing that makes a good trip is the crew, named in 85% of five star reviews, and it is the part you can least buy your way to.

When to go, and what to do there

Season is real but smaller than the advice suggests. The month-by-month picture in when to cruise shows the differences are modest next to the difference a boat makes, with one genuine outlier worth knowing about. On the water, the stops are more alike than the brochures pretend: the caves and islands guide counts which the fleet actually visits, and why the most famous ones are the most crowded.

The three questions that settle most of it

If you read nothing else, ask these before you pay, because they cover most of what goes wrong:

Is the Hanoi transfer included, and in what vehicle. What happens if a stop or a day is missed. And what is not covered by the fare once you are aboard, drinks especially. Three of 139 listings include the transfer, a cut itinerary is the sharpest marker of a bad trip, and surprise charges are the third of the three invisible complaints. Every one of those is answerable in an email, and the speed of the reply is itself a preview of the operator.

The catch, and what we cannot see

We should be plain about the edges of all this. Twenty of the seventy boats have no reviews we could collect, and a boat with no written record is not the same as a boat with a clean one. No operator publishes crew numbers or refit dates, so we cannot tell you the crew-to-guest ratio or the true condition of any boat, and any site that gives you those has estimated them. The review labels are machine-assigned, scored before we trusted them, and two of them under-count, so the complaint figures here are floors rather than exact shares. And a per-person price is a floor, not a quote: the number for your date and cabin lives with the operator and is almost always higher.

None of that is a reason to distrust the numbers. It is the reason we tell you where they stop, which is the one thing the pages selling you a boat will not.

Common questions

What is the most important choice? The boat, then the bay. Season and month matter less than either. A good boat in a fair month beats a mediocre one in the perfect week.

What is the biggest hidden cost? The Hanoi transfer. It is a three to four hour drive each way and it is in the fare on only three of 139 listings.

How do I spot a boat that will disappoint me? Not by the food reviews, which mean little. Read the newest reviews for cut itineraries, surprise charges and booking trouble, the three things that actually mark a bad trip.

Two days or three? A question about time, not money, because the three-day price is unpublished almost everywhere. Two days sees the headline of the bay; three days lets you spend time in it.