Meg Elkins swims in the Yarra early in the morning at Deep Rock, the bend in the river just before Dights Falls in Abbotsford, in Melbourne’s inner east. “The beauty of the place is extraordinary,” Elkins said. “We see a part of the river that no one else sees.

” Meg Elkins (left) and Holly Jones swim in the Yarra at Deep Rock. Credit: Jason South A sandstone cliff juts out of one side of the river, wattle trees flower along the banks and the mist rises off the water. The only giveaways that the swimming hole is four kilometres from the CBD are the hum of traffic from the nearby Eastern Freeway – and the water quality.

Elkins and the other “Yarra Yabbies” who swim at Deep Rock abide by a few basic rules: don’t put your head under, don’t swim when it’s flooded and don’t swim if you have an open wound. The same rules applied for competitors at the Paris Olympics, where some events in the Seine were delayed to allow the water quality to improve after heavy rain. Even with the precautions, some Olympians were left hospitalised and vomiting for days afterwards.

Paris spent €1.4 billion ($2.3 billion) to clean up the Seine before the Olympics, including building a giant basin to capture excess rainwater and keep wastewater from entering the river, renovating sewer infrastructure and upgrading wastewater treatment plants.

But concerns were still raised about the levels of E. coli and enterococci, indicative of sewage or fecal pollution in the water. Most str.