The 2016 Summer Olympics boating and swimming events have put an international spotlight on what has been a long-running problem in Rio de Janeiro—untreated sewage and trash are clogging up major bays and waterways, including the Guanabara Bay, where many of the boating competitions are being held.
A 2015 Associated Press study found that the nearly black water contained alarming levels of bacteria and viruses and could potentially make athletes who were exposed to it sick.