Bai Tu Long Bay, the quieter half of the karst

Bai Tu Long is the part of the bay the day boats do not reach: the same limestone towers in the same green water, northeast of the traffic. At the far end are islands you can sleep on.

What separates it from Ha Long Bay?

The two bays are one landscape with different routes through it. The karst does not stop at the edge of Ha Long Bay; it carries on northeast past Van Don towards the border, and a national park of about 15,700 hectares has covered the far end of it since 2001. The boundary between the two names is administrative rather than geological.

What changes is the traffic. A northeastern itinerary anchors where 2 or 3 boats are anchored rather than 40, and most of these cruises run two nights rather than one. It calls at fishing villages instead of the four fixed sights, and spends its second morning somewhere the day-trippers cannot reach. That is the whole of the difference, and for most people it is enough.

Which cruises are actually licensed for it?

Only some boats may sail this route, because the authorities licence an itinerary rather than a bay. That is the detail to check before booking. An operator advertising "Bai Tu Long" that sails the standard Ha Long circuit with one different anchorage is not unusual.

Ask which overnight anchorage the boat uses and which cave it visits. Thien Canh Son and Cong Dam are in the northeast; Sung Sot and Titop are not. The Ha Long Bay hub covers how to read a cruise listing generally, and Ti Top island is exactly the stop this route skips.

What is on Quan Lan and Co To?

Quan Lan and Co To are islands with roads, beaches, guesthouses and a Vietnamese summer season, and they are the alternative to a cruise. Fast ferries run from Van Don. Quan Lan is about 35 km out and an hour away; Co To is 80 km and closer to two hours. Nobody has built a resort strip on either.

Quan Lan and Co To are domestic holiday places: seafood, motorbikes for hire, long empty sand outside July and August. Few foreign visitors come, which is the appeal and also the limit. There is very little English, and the ferry timetable shrinks in winter.

What is Van Don, and why does it matter?

Van Don is the district the bay is named around, and it is the practical end of the route. The island has an airport with domestic flights, a deep-water port, and the ferry terminal every crossing to Quan Lan and Co To leaves from. Van Don is about 50 km beyond Ha Long city, an hour by road.

Van Don also explains the development question hanging over this corner of Bai Tu Long. Van Don was designated an economic zone and has been building casinos, resorts and roads for years, which is exactly what the quiet half of the karst was quiet for lacking. The quiet is real now and it is not guaranteed.

What is the sea like in each season?

The sea is calmest and clearest from October to April, and that window decides everything else about a trip out here. October and November are the best weeks of the year: dry, mild and past the storms, with the sea usually under half a metre of swell.

July to September is typhoon season on this coast. The port authority closes the bay when a storm is tracking, cruises are cancelled outright rather than shortened, and refunds depend entirely on the operator. The typhoon guide explains how much notice that usually comes with.

How do you get to the boat?

Getting out here means getting to Ha Long first, around two and a half hours from Hanoi on the expressway. The Hanoi to Ha Long guide covers the transfer options and their prices.

Cruise companies run their own shuttle from the Old Quarter, which is the simplest way and usually not the cheapest. For the islands rather than a cruise, the road goes further, to Van Don, where the ferries leave.

Is two nights worth it rather than one?

Two nights is the version of this trip that justifies coming, and it is what most Bai Tu Long boats sell. One night on any bay route means arriving at midday, one anchorage and leaving by nine the next morning. That is a five-hour round transfer for about eighteen hours on the water.

The second night is what buys the quiet water and the morning without other boats in it. If the budget only stretches to one, Cat Ba and Lan Ha bay are the better use of it. The island gives you somewhere to be when the boat is done.