Sailors, coaches and the mayor of Rio de Janeiro acknowledge the problem: Guanabara Bay, the venue for sailing at the 2016 Olympics, is badly polluted. Some liken it to a sewer.
The water is filthy after years of untreated waste being poured into the enclosed bay, a mess officials say will take at least a decade to fix.
From a distance, the venue is picturesque, framed between Sugarloaf Mountain and the Christ the Redeemer statue. This is the image Rio organizers want the world to see.
Yes, the venue will make good television. The conditions for the athletes? That's another story.
"A few days ago, one of the sailors had to jump in the water and the first thing he did after coming up was take a bottle of water and wash his mouth and face," said Ivan Bulaja, a former Olympian who coaches the Austrian team. "When you feel this water on your face you feel uncomfortable. You have no idea what's in it. I think no sailor is comfortable sailing here. I guess you can get seriously ill."
But sail they will, starting Sunday with the first test event of the Rio Games. The weeklong regatta will feature all 10 Olympic classes, with 216 boats and 321 competitors from 34 nations.
Rio dumps almost 70 percent of its untreated sewage into the surrounding waters. Cleaning the bay was part of the pitch to land the Olympics, with officials pledging to cut the flow by 80 percent by 2016.
But Rio's state environment secretary, Carlos Francisco Portinho, has acknowledged in a best-case scenario the reduction will be only 50 percent.
Rio de Janeiro Mayor Eduardo Paes acknowledged two months ago that the problem would not be solved for the Olympics.
"I'm sorry that we did not use the games to get Guanabara Bay completely clean," Paes said. But he added he was "not afraid for the health of any of the athletes. It's going to be fine."
A series of stopgap remedies are being put in place -- rubbish boats to retrieve floating debris, and barriers to stop sofas, wooden chairs and plastic bags from entering the bay in the first place.
Rio state environment officials said in the first three months of the year, three boats retrieved 33 tons of solid waste. Ten will be operating for the test event.
The other problem is less visible: untreated human waste, which can't be retrieved and leaves a stench all around the bay.
"At low tide, it smells like sewage water. It smells like a toilet," said Austrian sailor Nikolaus Resch, who finished fourth at the London Olympics in the 49er class with teammate Nico Delle Karth. "You see people going for a swim. I would never -- under free will -- go in the water here."
At a small regatta last year, sailors were seen using alcohol to clean their hands after leaving the brown-black water, often capped with green foam.
To allay fears, the International Sailing Federation and local organizers are encouraging teams to test the water around the course areas. Rio state environment officials describe these areas as "suitable for swimming."
State environment officials say they monitor fecal coliforms monthly, but have been doing it every two weeks since June to prepare for the regatta.
Tides, shifting currents and rainfall mean parts of the heavily industrial bay are cleaner than others, and several race courses are located just outside the bay in the open Atlantic.
"A lot of people have been talking about pollution," Alastair Fox, head of competitions for the sailing federation, said in an interview with The Associated Press. "It would be nice not to be able to talk about that. But we all know that it's there. We need to make sure that as much is done as possible to make a safe and healthy venue."
Fox said the ISAF was making no health recommendations, although a physician contacted by AP said all sailors should be vaccinated for hepatitis A. Other waterborne diseases like diarrhea and gastroenteritis can be picked up in dirty water.
Fox said many sailors were more worried about floating furniture, submerged trash bags and streams of flotsam fouling their rudders, than they were about human waste.
"Presuming the water quality is OK, as in the sewage levels, for us it's imperative we have a clean field of play," Fox said. "We can't have a field of play with any objects in it that impact on the sailors' ability to race."
