Rio de Janeiro's Olympic bid included a promise to clean up the filthy waters of Guanabara Bay, venue for sailing events during Rio 2016. However, with less than two-and-a-half years to the start of the games, the water is contaminated with dangerous levels of raw sewage, and its beaches are littered with rubbish.

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A man walks past rubbish on Botafogo beach, with Sugar Loaf Mountain in the background Reuters

City authorities had planned to treat 80% of Rio's sewage, but Gelson Serva, Deputy State Secretary of Environment says only 34% of its human waste is treated - the rest goes into the bay.

There are more than eight million people in the 15 cities surrounding Guanabara Bay, producing over 18,000 litres of sewage per second. Leona Deckelbaum of the NGO, My Rio, told the BBC the level of faecal matter in the bay is 198-times higher than the US legal limit. "I wouldn't put my little pinky toe in it," she said.

There are fears that the water is unsafe for swimming and will be too polluted to host Olympic events.