It is only 17 months until the 2016 Olympic Games which is set to be held in Rio de Janeiro, Brazil but the city is still quite a mess.
Organisers had set a target of cutting the amount of untreated sewage flowing into it by 80%. It is thought they are achieving around 48%.
Several Olympic-medal winning sailors have said Guanabara Bay is the dirtiest place they have ever competed, citing incidents of dodging floating sofas, plastic bags and even dead animals.
In February, thousands of dead fish were found in Guanabara Bay. Fish die-offs are also common in Rio's Rodrigo de Freitas Lake, where the Olympic rowing competitions will be held.