This postcard setting, one of the best known in Southeast Asia, is a victim of its success. Its beauty is marred by debris from buoys, plastic bottles and other soda cans that litter the sea, between the famous limestone blocks.
Ms. Thinh has been sailing the bay on her boat for 10 years trying to contain the impact of human activity on this Vietnamese UNESCO World Heritage Site.
"I have to do five to seven boat trips every day to pick everything up," she told AFP.
Four Olympic swimming pools
In the past three months, 10,000 cubic meters of rubbish — enough to fill four Olympic-sized swimming pools — have been collected from the water, according to the Ha Long Bay Administration Department.
The situation is particularly critical since a recent conflict between fishermen led some of them to dispose of their old Styrofoam buoys by throwing them overboard.
Workers collect garbage with a landing net in Ha Long Bay, Vietnam, on May 17, 2023 © Nam NGUYEN / AFP
Twenty barges, eight boats and a team of ten people were then deployed by the authorities urgently to clean everything, according to state media.
Beyond this specific problem, "Ha Long Bay is under pressure," admits Do Tien Thanh, in charge of the conservation of the site.
In 2022, more than seven million visitors came to admire the spectacular limestone karsts topped by tropical vegetation on Vietnam's northeastern coast.
The authorities are hoping for eight and a half million this year.
Cable car, amusement park, luxury hotels: the city of Ha Long has bet all its economic development on tourism, but the consequences on the marine ecosystem are already visible.
In the bay, there are only a hundred types of corals left, compared to twice as many originally, according to conservationists, even if the ban on fishing in some areas has corrected the situation.
A boat carrying tourists in Ha Long Bay, Vietnam, May 17, 2023 © Nam NGUYEN / AFP
Dolphin populations have been observed, a first in 10 years.
"Plastic pollution crisis"
Single-use plastics have been banned on board tourist boats, but man-made waste remains a major concern, as "there are many residential areas near Ha Long Bay," the conservator said.
And the municipality does not have the means to properly treat all this domestic waste.
Some wash up in quantity on the beaches, at the sight of stunned tourists.
A pile of garbage collected in Ha Long Bay, Vietnam, May 17, 2023 © Nam NGUYEN / AFP
Larissa Helfer, a 21-year-old German tourist, acknowledges that Ha Long Bay is beautiful, but that the waste problem is one of the most memorable memories of her trip to Vietnam.
Normally, one should say to oneself: "Look at the view! Look at the fishing villages," she told AFP.
But here, "you have to talk about garbage, (you say) +Oh my god... Look at plastic bottles and things in the sea+. And that makes you sad."
"My clients read in the media that Ha Long Bay is beautiful, but when they see the many floating waste, they no longer want to swim or canoe there and they hesitate to recommend their friends and family to come," says Pham Van Tu, a local guide.
Rapid economic growth, urbanization and changing lifestyles in communist Vietnam have led to a "plastic pollution crisis," according to the World Bank.
A report published in 2022 found that the country is among the top five ocean polluters in the world, with 3.1 million tons of plastic waste produced each year, at least 10% of which ends up in water.
Waste collected with a landing net in Ha Long Bay, Vietnam, on May 17, 2023 © Nam NGUYEN / AFP
This figure could more than double by 2030, warns the institution.
On her wooden boat, trash piles up around Mrs. Thinh who remembers a very different bay when she was a child 50 years ago.
"It looked different," she says.
"Of course, this job tires me and makes me angry," she admits. "But we have to do it."
© 2023 AFP