A stout green catamaran plies the polluted waters of Rio de Janeiro's Guanabara Bay alongside wooden fishing boats, but its catch consists of plastic bags, drink bottles and a discarded toilet seat.
The catamaran is one of three so-called "eco-boats", floating garbage vessels that are a key part of authorities' pledge to clean up Guanabara Bay before the 2016 Olympic Games. But critics say the boats do little to address the more pressing question of sewage.
With limited trash and sewage services in the sprawling metropolis of six million people, tonnes of garbage and raw waste flow daily from sludge-filled rivers into the bay, where Olympic and Paralympic sailing events will be held.
At low tide, mountains of household refuse, old sofas and even washing machines are seen.
An analysis last year of more than a decade's worth of Rio state government tests on waterways showed faecal coliform pollution levels far above those considered safe by Brazilian or United States law.
That pollution means nearly all beaches dotting the 383sq km bay have long been abandoned by swimmers, and some health experts warn of risks to athletes who come into contact with the water. Elite sailors have warned that high-speed collisions with floating detritus could damage or even sink sailboats during the Olympics.
Water pollution issues began making headlines after thick patches of brown foam appeared along the city's most popular beaches such as Copacabana as summer hits full stride. Rio's beaches, overwhelmed with holiday visitors, have been inundated with trash, much of it floating in water near the sand.
That is where authorities hope the eco-boats will make an impact. Rectangular steel craft fitted with powerful speedboat motors, the vessels use a sieve to trap garbage floating up to 45cm below the surface, capturing everything from household trash to abandoned television sets and refrigerators. The trash is dumped into the boat, where recyclables are sorted out.
The barges don't address sewage, but authorities insist they will make a big dent in the overall pollution.
"Our objective is to not have floating garbage in Guanabara Bay," said Gelson Serva, who heads the state government's latest bay cleanup programme, a US$840 million ($1018 million) project that includes efforts to expand the capacity of the city's strained sewage treatment system.
Only 30 per cent of Rio's sewage is treated, and the rest flows into rivers, the bay, local lagoons and its world-famous beaches.
"Those who live around the bay can already notice a difference over the past two years," Serva said as the clanking sieve dumped garbage into the ship's hull.
Three boats with the capacity to hold 3.5sq m of trash will be joined by six small boats and one large barge by March.
Mario Moscatelli, a biologist and outspoken environmentalist, said the eco-boats were a positive step in the right direction, but were too little, too late.
"At this point, for the patient that is Guanabara Bay, over-the-counter medicines won't do. What's needed now is chemotherapy, radiotherapy, definitive action."
Moscatelli said the major rivers flowing into bay should be fitted with heavyweight "eco-barriers" to filter out the garbage at the source. Existing "eco-barriers" on some rivers were too flimsy and allowed most of the trash through, he said.
"This sort of manual collection is great for photos," he said of the boats now gathering trash, "but it doesn't even begin to address the root of the problem."