Finding bodies isn't unusual. Often it's an animal. About once a week, it's a human. Decaying remains, fetid sewage and floating garbage in Rio de Janeiro's waterways are fuelling worries about water safety ahead of the Olympics. Seven years after being awarded the Olympics, the massive seaside city has only managed to decrease, but not end, the dumping of garbage and untreated sewage into its waterways.

These are the same waterways where some Olympic rowers and sailors will now compete. Worse yet, where the open-water swimmers will charge into the water to swim 10 kilometres. The best advice they've been given: Keep your mouth closed.

The problem is obviously floating garbage. - Mario Andrada, Rio 2016 spokesman

"The problem is obviously floating garbage," Rio 2016 spokesman Mario Andrada told the CBC's David Common. "There are high-performance boats going through here, you cannot afford to have a piece of garbage affecting their performance."

The solution — at least in Guanabara Bay — has been to fence off the 11 rivers flowing into the bay. Garbage is trapped behind the fence, but it needs to be cleaned out at least daily. When it rains, the river flow becomes so fast, the garbage pours over the fence line.

The problem originates, though not exclusively, in the city's poor favelas. Sanitation is rudimentary, the people desperately poor, and for years they've thrown their waste in the rivers. The current takes away garbage that government often won't. And while commercials on radio and television urge residents to stop polluting the water, it's a habit now and there aren't always alternatives.

Unable to tackle the problem upstream, organizers are now using booms to contain and collect debris in the water.

The bid document submitted by Rio in 2009 says the games would 'regenerate Rio's magnificent waterways.' The city has long struggled to clean up pollution in the area's water. (CBC) Seven years ago, Rio treated just 17 per cent of its sewage. Rio 2016 organizers pledged to treat 80 per cent of sewage by the time the Games opened, and the city and other levels of government ploughed a billion dollars into sanitation projects, many of which are still unfinished or not working. Of eight treatment plants promised, only one ever got built. Today, the city is treating about 50 per cent of its sewage, Common reports.

"They said everything to win the Olympic Games," biologist Mario Moscatelli told the CBC's Adrienne Arsenault. But they "said one thing and they did another thing," he said.

Moscatelli showed CBC News the scale of the problem from a helicopter. Long lines of sewage can be seen flowing from streams and rivers into bays and lagoons.

"This is a shame!" Moscatelli says as the helicopter passes over an area with visible sewage near the Olympic Park.

"We have money, we have technology, but we don't have interest," says Moscatelli, who has been tracking the sewage situation in Rio for 20 years and has been active in the campaign to clean up the waterways.

The International Olympic Committee knew progress wasn't being made. It checks in regularly on cities hosting future Games. But so much else was behind schedule, including accommodation and transit.

A water quality survey of the aquatic Olympic and Paralympic venues commissioned by The Associated Press 'has revealed consistent and dangerously high levels of viruses from the pollution.' (CBC) The Associated Press has, for 16 months, tested Olympic aquatic venues and found them contaminated and teeming with harmful bacteria as well as viruses at "consistent and dangerously high levels" that would almost certainly sicken athletes who ingest just three teaspoons' worth of water.

Canadian rowers did get sick at a test event in Rio months ago, but the cause was believed to be bad popcorn at a stadium, not contact with the water. Nonetheless, many athletes are bleaching their oars after use. Sailors have talked about wearing disposable coveralls and gloves at the start of their race — where the highest concentration of raw sewage is found.

"We would never, ever risk the health or condition of any athlete," Andrada said. "I can guarantee in the name of Rio 2016 that the athletes can compete safely."

If bacterial tests show a dangerous area, Andrada added, events can be shifted to less polluted zones.

Watch the video above to learn more about the challenges in Rio and to get a view from above of the city's water pollution.