Rio 2016 officials tells athletes: the water's fine

The waters off Rio de Janeiro will be safe for Olympic open-water swimmers, sailors and rowers, the Rio organising committee insists, after new tests showed reduced levels of pollution.

"We can guarantee athletes' health," said Rio spokesperson Mario Andrada on Tuesday.

He said athletes will get daily updates on water quality ahead of events.

Rio has struggled to rein in high levels of pollution in the waters of Guanabara Bay, where Olympic sailing competitions will take place, and in the waters and lagoons off Copacabana Beach, which will host open-water swimming and rowing events.

Reports of dead bodies, furniture and raw sewage in Guanabara Bay have made headlines around the world, and athletes have expressed concerns about coming into contact with the water.

German sailor Erik Heil was infected by a flesh-eating bacteria in his foot and hip last year after a visit to Brazil. Doctors linked the infection to his participation in practice events on Guanabara Bay.

Sailors have prepared with extra vaccinations and plans to rinse off the muck from their boats with fresh water.

A system for keeping sewage out of the Marina de Gloria, the starting point for Olympic sailing events, has made progress, and garbage-scooping "eco-boats" will take care of floating waste.

Organisers originally had planned to treat 80 per cent of the water in Guanabara Bay by 2018 - a goal which would require stopping the flow of raw sewage into the bay from Rio's homes, factories and hospitals.

At least half of the bay's water would be treated for now, Andrada said, which would be an improvement over the mere 12 per cent treated when Rio was awarded the Games in 2009.

The Inter-American Development Bank (IDB) approved a loan of more than $US450 million in 2011 for cleaning up the bay in time for the Games.