Is there phone signal on a Ha Long Bay cruise?
Near shore and on the main routes, mostly yes, with Viettel the most consistent. Deep among the karsts some named spots still have none, though new towers went up in 2026.
On most of the main cruise routes, yes, with gaps deep among the islands. Viettel is described as the most consistent network on the bay, MobiFone as decent on cruise routes, and Vinaphone as less stable offshore. Vietnamese authorities list a handful of spots that still lack adequate signal, and coverage is improving through 2026 as new towers go up.
Our Vietnam eSIM connects to Viettel, MobiFone and Vinaphone, so on the bay it can use whichever of the three reaches you.
Where signal is still weak
In September 2026 the Vietnamese press listed these places without adequate coverage: Hang Luồn, Hang Trống, Hòn Đỉnh Hương, Vụng Cặp Táo, Vụng Tùng Sâu, Trà Sản, Cát Lán and Hang Cỏ. Viettel switched on new towers at Vung Viêng and Cống Đỏ in early 2026, covering roughly 10 to 15 km around each.
Cruise Wi-Fi
Onboard Wi-Fi on most boats runs over the same mobile networks, shared by all passengers, so it drops where the signal drops. The sundeck usually gets the best reception.
What to prepare
- Download offline maps and your cruise booking before you board.
- Expect a quiet hour or two in the caves and deep bays.
- Upload photos back near the harbour or in Hanoi.
Quick answers
Is there Wi-Fi on Ha Long Bay cruises?
Usually, but it runs on the mobile network and drops between islands.
Which network is best in Ha Long Bay?
Viettel, according to local reporting and SIM sellers, then MobiFone.
Is there signal in the caves?
Several caves and coves are on the official list of places without adequate coverage.
Sources: CafeF (2 September 2026), Dân Trí (17 March 2026), Kênh 14 (5 June 2024). Checked 21 September 2026.