Best way to get to Ha Long Bay from Da Nang, Vietnam
Ha Long Bay is 760km north of Da Nang
The best way to get to Ha Long Bay from Da Nang is to fly, which can be done very cheaply. The only alternative is to take a train to Hanoi then transfer another 180km to Halong Bay
Flight options from Da Nang to Halong Bay:
This is the recommended option because it beats the alternative by a huge margin in both cost and time
The best airport to fly to is Cat Bi International Airport in the city of Hai Phong, because it's located only 50km away. Some people also fly to Hanoi's Noi Bai International Airport because they think it's a hub, but it's much farther at 150km away and takes 3.5 hours to transfer to Ha Long Bay
There are 3 daily direct flights from Da Nang to Ha Long Bay
8:10am -> 9:25am with Vietjet Air
12:05pm -> 1:20pm with Vietnam Airlines
5:10pm -> 6:25pm with Vietjet Air
Flight time is 1 hour and 15 minutes
Airfare:
Fare for Vietjet Air is the cheapest at $25 USD per person each way
Vietnam Airlines is more expensive at $45 USD per person each way because it's a full service airline
However, with Vietjet Air you will have to pay baggage fee, which is about $7 USD for under 15kg, and $14 USD for 20-25kg
Departure airport is Da Nang International Airport, which is located very close to the city and only costs a few USD to get to by taxi
After you arrive at Cat Bi International Airport:
You will need to take either a taxi or private transfer to take you to Tuan Chau harbor, which is the starting point of many Ha Long Bay cruises, or the town of Ha Long, where all the hotels are
This will take about 70 minutes
Taxi from the airport to the harbor will cost you $40-$50 USD each way
Private transfers will cost around $60 USD
Train to Hanoi, then transfer to Ha Long Bay:
I do not recommend this option because it takes too long and is more expensive than the flight option
To be more specific:
Train from Da Nang to Hanoi takes 16-17 hours and cost a minimum of 509,000 VND ($21USD) per person on a 2nd class seat. For this duration trust me you will want a berth, which will cost you $30USD for the top bunk of a 6-room compartment. The most expensive bed, which is the bottom bunk of a 4-room compartment, will run you 921,000 ($40USD)
Once you get to Hanoi, you will need to transfer to Ha Long Bay. You have several options:
Take a train from Hanoi to the town of Hai Phong (the same town as the airport in the flight option mentioned above). This will be your best option because it only takes 2 hours and 40 minutes, and cost you $2-$3 USD for a seat
Alternatively, you go by shared bus ($10USD) or private transfer ($90USD). The advantage of this is that it will drop you off at your final destination, rather than Hai Phong train station where you still have to transfer by taxi to your final destination. But you will likely need to book your shared bus or private transfer ahead of time, and coordinate with them to pick you up from the train station
As you can see, it's extremely cumbersome to use this option. Altogether, you will end up spending 36-48 hours to get to Ha Long Bay, and spend 2-3 times what you would spend with the flight option