But now, it may cost one European a medal, after she apparently got a bacterial infection from the water.
If you're watching the Olympics on TV, Rio's Guanabara Bay looks like one of the most beautiful places on earth. But up close, it looks a bit different.
Wil Van Bladel is head coach of the Belgian sailing team. He said his star sailor, Evi Van Acker, has been diagnosed with a severe intestinal infection. The team's doctor believes she got it from polluted water in the bay. Her coach said she's so weak, he doesn't know if she can be competitive.
"Did you expect her to win a medal here in Rio?" Tracy asked.
"I was almost certain," Bladel said. "She would've been really capable of winning the gold."
Extreme water pollution has been a big black eye on the Rio Games, with some even calling it the "poop Olympics." But just before the games, the International Olympic Committee released a statement, saying: "Rio is ready to welcome the world" and touting "much improved water quality."
When we visited Rio in June, we saw trash covering parts of the bay and a giant plume of sewage flowing into the marina, where Olympic sailors are now launching their boats. About 1,400 athletes are now competing in water-based events in Rio, and some will have to swim in it.
But not Renato Picao, a microbiologist who took us to parts of the bay near the Olympic events and said she would never swim in the water. Her scientific tests show alarming levels of super bacteria - the result of both sewage and medical waste from hospitals.
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"Almost half of what we generate goes raw into our water bodies and definitely goes to the bay and then to the beaches," Picao said.
"And that's essentially like just flushing a toilet into the water?" Tracy asked.
"Yes," Picao answered.
In order to get the Olympics, Rio promised to install eight treatment plants on the polluted rivers entering Guanabara Bay. It built one.
Rio also promised to treat 80 percent of the sewage entering the water, but is treating just about half. Those broken promises might cost Van Acker an Olympic medal.
"She had tears yesterday evening. She was emotional because she worked so very hard for it," Bladel said.
Rio Olympic officials call Van Acker's case an isolated accident. The state environmental department said it is testing the water in Guanabara Bay every day and claims it's good - even safe enough to swim in. But when asked to see the test results, they would not show us any from since the games began.