A major challenge on the road to Rio 2016 has begun this weekend with the start of a week-long sailing test event, the first such event to be held in any sport, on the waters of Guanabara Bay.
This comes as Rio 2016 still battles to provide reassurance over many aspects of preparations for the Games in two years time, after much criticism.
The week-long competition is taking place amid a cloud of concern over pollution levels on the course, after it was revealed last November that Guanabara Bay has 78-times Brazil's legally allowed limit of fecal pollution, and 195-times the United States limit,
Earlier this year International Sailing Federation (ISAF) head of competitions Alastair Fox admitted to insidethegames that holding the test event would be "difficult" as planned measures to deal with the pollution would not have come into operation.
In the build-up, concerns have also been voiced by a large number of participants, and most recently by 49erF class world champions Alex Maloney and Molly Meech of New Zealand, who said they had their fingers crossed they will avoid illness when they compete.
This is particularly because larger-scale measures aiming to rectify problems, such as a giant "containment belt" to protect the specific sailing venue at Marina da Gloria, will not come into operation until shortly before the Games.
So far, success has been reported, with 324 athletes, including 23 Olympic medallists, participating from 34 different countries.
This included Dorian van Rijsselberge of The Netherlands and Charline Picon of France, the respective leaders of the male and female R:SX classes after the opening day of action.
Sailors have also been invited to test pollution levels on the course, in the interest of transparency, with the USs among those to have hired medical experts so as to do this.
US Sailing managing director, Josh Adams, said that tests had shown the water was "contaminated", but remained generally upbeat about the event.
"We feel our sailors are safe, and we're aware of the issues with the water quality in Guanabara Bay," he said.
"We know and have proven with our own water testing project that the water is contaminated, but we didn't discover anything that people didn't already know.
"It's contaminated largely because of unregulated sewage."
"I can tell you with assurance that our training hasn't at all been affected by the water conditions.
"Good sailing inside Guanabara Bay and outside the bay."
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July 2014: Rio 2016 inviting sailors to test pollution levels as Guanabara Bay course criticised again
June 2014: Rio Mayor admits water pollution targets in Guanabara Bay will not be met in time for Olympics
May 2014: ISAF considering independent testing to study pollution levels ahead of Rio 2016 test event
May 2014: Exclusive: Rio State Government claim measures being taken to tackle pollution ahead of sailing test event
April 2014: Exclusive: Rio 2016 test event will be "difficult" due to polluted waters, admits ISAF official