Rio de Janeiro's water quality needs to dramatically improve ahead of the 2016 Olympic Games, which will be hosted in the former Brazilian capital.
According to oceanographer Vinicius Palermo, Guanabara Bay, which is a likely destination for the sailing events, is in an appalling state.
He runs a specially-designed boat up and down the coast, filtering out as much as 80kg of rubbish per trip.
Mr Palermo noted that Rio's water quality is so bad because only a third of the city's wastewater is treated before being dumped in its 19 rivers.
Alex Grael, president of an environmental cleanup and education programme called Projeto Grael, said that if the Games were today Rio would be offering some of the poorest sailing conditions in history.
"If one of these boats, during the competition, were to get tangled in plastic, it would be a real embarrassment for the bay and for the city," Grael claimed.
London is also under fire for not addressing the problem of low air quality ahead of next year's Olympic Games.
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