Cho complained of dehydration, vomiting, a headache and dizziness when competing in the event, prompting his coach Danny Ok to claim the cause is "probably from the water".

Cho returned to the competition the next day and he is said to be one of a few sailors to have contracted an illness as a result of the polluted water, which is littered with debris including dead animals and other rubbish, with others preferring to remain anonymous.

Rio 2016 disputed the allegations from Ok, who also described the water as "smelly".

They claimed "there was no direct evidence to suggest the illness was caused by contact with water".

They added in a statement: "From a field of 326 athletes and 68 technical officials on the water, the International Sailing Federation (ISAF) medical team has received only two medical cases over the first five days of competition.

"ISAF have confirmed this number is significantly below the average for a regatta of this size.

"From a field of 326 athletes it is normal for some athletes to experience illness when travelling and competing in new environments."

Mexico sailing coach Agustin Bellocchio even went as far as telling sailors competing in the test event, which began last Saturday (August 15) and is due to finish on Saturday (August 22), to "shut their mouths" when out on the water in order to avoid contamination.

"Shut your mouth when you're in the bay, and don't take in any water," he said.

"Everyone knows this bay is badly contaminated."

Nebojša Nikolic, a member of ISAF's Medical Commission, has been in attendance at the competition to speak with the International Olympic Committee (IOC) and organisers on how to ensure the safety of surfers when the Olympic Games come to Rio de Janeiro in August of next year.

Sailing’s governing body maintain that attempts are being made to clean the waters by closing landfills, reducing industrial pollution, increasing water treatment works, and reducing floating garbage.

Authorities in the Brazilian city had originally vowed to remove 80 per cent of the waste but admitted recently that this wasn’t a feasible target, prompting calls to switch the venue for the sailing events at the Olympics to a different location.

The development comes after 15 members of the United States team were also taken ill following the rowing test event on the similarly polluted Lagoa Rodrigo de Freitas, although organisers claimed this was unconnected with the water.

The issue of the state of Guanabara Bay, which will host sailing competitions at next year’s Olympics and Paralympics, has been a constant thorn in the side of organisers, with IOC President Thomas Bach admitting it was a "serious challenge".

Recent independent tests also found the waters, which contain around 70 per cent of Rio’s raw sewage, could pose a "serious health risk" to athletes.


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