But with just days left until the Games start, studies have found the waters on which some of the world’s best sailors will compete are contaminated by viruses and drug-resistant superbugs.
Scientists at the Federal University of Rio de Janeiro carried out tests in areas including Guanabara Bay — the sailing venue — over the course of a year.
They told CNN they had found the highest level of superbugs of the sort found in hospitals on the shores of the bay, with pollution problems also evident on tourist beaches.
“We believe hospital sewage gets into the municipal sewage and then gets to Guanabara Bay and finally to the beach,” Renata Picao, a professor at the university, explained.
Water pollution in Guanabara Bay has been a problem for decades because of limited sanitation and sewage treatment facilities in Rio and the surrounding areas.
Sewage and debris including plastic, clothing and even dead animals, creates rafts of rubbish that contaminate and could even pose a collision hazard for boats.
Spanish sailor Fernando Echavarri told CNN the waters were the dirtiest he had competed in and warned: “As soon as you cut your foot you can easily infect yourself — and that is a problem.”
Erik Heil blamed water pollution for a skin infection suffered while training with Germany’s team, although it was not confirmed whether the water had been the cause.
However, Josh Adams, the managing director of U.S. Sailing, told CNN his team had trained extensively in Guanabara Bay “with no major incident.”
Australian Chef de Mission Kitty Chiller has also addressed the water quality in Rio and said the team’s athletes were “getting on” with their training while taking precautionary measures such as good hygiene and probiotics.
“At this point in time, we ain’t going to change the water quality in the next week so they’ll just get in and do their best,” Chiller told reporters.
Authorities in Rio insist there is an “internationally acceptable” level of bacteria in the water.
“We would never risk the health or condition of any athlete for a competition,” Mario Andrada, chief spokesman for the local Olympic organizing committee, told the Associated Press (AP).
“So the health of the athletes is our first priority, and the athletes don’t run a risk sailing in Guanabara Bay.”
However speaking to CNN in June, scientist Mario Moscatelli claimed the waters in and around the bay were “dangerous.”
Rio-born Moscatelli, an environmental biologist, said: “We have garbage from houses, garbage from hospitals.
“All the sewage, all the trash, when the tide is low, floods in that direction,” he added, pointing from a tributary in the direction of Rio.
“If you have the low tide, rain and wind inside to outside Guanabara Bay, then we have a big problem.”
He added that although he had been born in the city, he would ‘never swim in this water,” branding it “dangerous.”
Plans to revamp Rio’s infrastructure, including massively upgrading its sewage and water-cleaning capabilities, have been dented by the economic downtown that has affected Brazil since the Games were awarded.
Almost 13 million people live around the bay in Rio, and the current sewage system can struggle to cope.
Olympic organizers said emergency measures were in place if the water quality were to become dangerous at any time during the Games.
Contingency plans could include changing the times of sailing events — pollution is worst in the mornings — or the location of the launch area.
“Athlete safety is our priority,” Tania Braga, the head of Sustainability and Legacy at Rio, told CNN.
“We are going to do daily tests during the games and we do not expect to have any problems of non-conformity in the race areas, but we are prepared with contingency measures if needed.”
On Monday, the findings of a 16-month AP survey of the aquatic Olympic and Paralympic venues showed a high levels of viruses and led biomedical expert Valerie Harwood to warn: “Don’t put your head under the water.”
The study revealed major contamination at the Rodrigo de Freitas Lagoon — where rowing events will take place — and the Gloria Marina, the launch point for the sailing regatta.
It showed the situation had worsened in some areas, with levels of adenoviruses in the water having gone up despite attempts to prevent sewage from reaching the marina through storm drains.
Samples taken last March showed 26 million adenoviruses per liter of water, but this June the level hit more than 37 million adenoviruses per liter, meaning athletes who took in the equivalent of just three teaspoons of that water would become infected.
But a Rio 2016 statement said: “Rio 2016 confirms that the fields of play for all water sport competitions meet all the relevant standards set by the World Health Organisation and ensure a safe and fair competition.
“For sailing, we held two successful test events in August 2014 and August 2015 and a medical survey conducted by the international federation, World Sailing, found the event to be above average in terms of athlete health.”
In June, Rio mayor Eduardo Paes, who recently opened a new sewage treatment plant, told CNN he was confident that the Olympic sailing area would be safe for athletes.
But he said: “Don’t come here expecting that everything will be perfect. We live in a country that has an economic crisis, a country with lots inequality. But the city will be much better than it was when we got the Games.”