AT least 35 people have died after a packed tourist boat capsized on a sightseeing tour in Vietnam.
The Wonder Sea boat had 49 people - including five crew members - on board in Halong Bay when a "sudden" storm flipped the vessel.
Officials revised down the death toll to 35 from an initial 38 - with 10 survivors rescued.
Rescuers are still scrambling to find four missing people.
Pictures from the scene showed stormy skies as rescue boats surrounded the capsized vessel - with divers in the water scrambling to find survivors.
It's understood at least three tourists were rescued by a passing boat.
And a 14-year-old boy was rescued four hours after being trapped in the overturned hull.
Bui Cong Hoan, deputy head of the Halong Cruise Ship Association, said: "Although the ship had overturned and the cabin doors were locked, there was still an air pocket about 50 to 60cm wide, enough for oxygen to get in, so the boy survived."
The boat overturned near Dau Go Cave around 1.45pm local time on Saturday - with around 20 children on board, reports say.
Most passengers were reportedly from Hanoi, travelling as families - with the oldest being 53 and the youngest just three.
All the tourists aboard were Vietnamese, including several children, the official Vietnam News Agency said.
Rescuers have been battling stormy weather - with thunderstorms and downpours smashing the bay.
It came shortly after Storm Wipha hit the South China Sea, bringing strong winds, heavy rainfall, and lightning.
It's the third typhoon to hit the South China Sea this year - and it was set to make landfall along Vietnam's northern coast early next week.
Halong Bay, situated roughly 125 miles northeast of Hanoi, is dotted with nearly 2,000 islands.
It's designated as a UNESCO World Heritage Site - attracting tens of thousands of visitors every year.
Many companies offer overnight boat tours in the area.
A tour boat sank in Halong Bay in 2011, killing 12, with foreign tourists among them.