Swiss tourist Alex Brauwalder expressed his disappointment at the garbage during his tour of Ha Long Bay - Lan Ha Bay - Cat Ba Island in mid-February.
Some floating plastic waste stretched several hundred meters long, so he could not swim in the bay, he said.
Patricia Mayerhofer, an Australian tourist, visiting Ha Long Bay from Feb. 20 to 23, said that the world heritage site looked like a "sea of trash."
She was told by tour operators that the trash came from fishing villages or was dumped by tourists.
"I see that Vietnam doesn't really care about environmental issues," she said.
Ged Kelly, a British tourist, shared a similar experience. While kayaking for 20 minutes on the afternoon of March 4, Kelly saw "countless plastic bottles, cans, gloves, even an office chair floating on the water."
More plastic waste tends to appear in Ha Long- Cat Ba Island area, famous for cruise tours and kayak activities, from September to May, coinciding with the international tourism season.
The management board of Ha Long Bay said in early March that floating trash was mainly scattered in Trong Mai, Me Cung, Sung Sot, and the Luon Caves.
Due to the foggy, humid, and windless weather, trash and foam float from the foothills, rocks, and banks.
Since the end of February, sanitation workers have been collecting waste from early morning to 5 p.m., averaging about 10-12 blocks of trash per day.
In early March, the management board mobilized nearly 20 ships, boats, and ferries to collect floating trash to shore for processing.
It will continue to strengthen inspection and supervision and handle violations of waste and wastewater management and environmental protection in Ha Long Bay.
However, Hoang Minh, owner of the cruise ship that Brauwalder rented, said the garbage problem in Ha Long Bay and Cat Ba "has persisted for many years," even though there have been garbage cleanups.
Nguyen Duy Phu, chairman of Lan Ha Cruise Association, said tourists would not accept any appeasement from boat owners regarding the issue.
No matter how good the service is, the tourists still give zero satisfaction points because the bay was full of trash, Phu added.
To limit the bad experiences of foreign tourists, his association has hired its own boats to clean up the trash three times since last year.
Fodor's Travel magazine recently included Ha Long Bay in its annual list of destinations tourists should re-consider traveling to due to its trash problem.
Brauwalder said it was necessary to strictly deal with the source of plastic waste in Ha Long Bay and Cat Ba Island and international tourists like him are willing to pay more to support efforts to clean up the heritage area.
"If there is not a serious effort, international tourists will turn away from this location in a few years. Let's pay attention to big problems instead of short-term benefits," Brauwalder said, adding that he had sent a petition to UNESCO on the pollution problem in the Ha Long Bay - Cat Ba archipelago.