Environmental experts are telling Victorians to head to the swimming pool over the weekend instead of the beach, with water quality across the state still poor after recent flooding.
Widespread flooding across the state in October has led to stormwater pollution throughout Victoria's river systems.
Environmental Protection Authority chief scientist Mark Taylor said microbes from across the state make their way into the water system after heavy rains.
"When there's a flood, often sewerage systems and faeces from domestic animals, agricultural animals and native animals will be washed into the river," Professor Taylor said.
"You can see that when you go down to the bay. The water's cloudy. It's dirty."
Potentially toxic trace metals such as arsenic, lead and zinc, along with carcinogenic chemicals and bacteria — including E. coli and Enterococci — are found in flood waters.
Concentrations of E. coli bacteria were found via EPA testing in the Maribyrnong River last week after substantial flooding.
Exposure and infection with E.coli bacteria can result in stomach cramps, diarrhoea, nausea and vomiting.
The EPA has this week extended its sampling range in collaboration with the SES and will test for contaminants in 16 regional Victorian locations.
Expert urges 'precautionary approach'
With temperatures expected to reach the mid-20s across much of the state, Victorians may be tempted to take a dip at the beaches around Port Phillip Bay.
However, Professor Taylor said would-be swimmers should take a "precautionary approach" and avoid bay water.
Microbes and trace metals can be washed downstream as a result of flooding
He said it could take weeks for the water quality to return to its previous acceptable levels.
"The pollution — or poor water quality — is moving from upstream to downstream, so it will be some time before the beaches start to display suitable or good quality acceptable for swimming,
"I would wager it's probably not going to be suitable until at least next weekend, until the very earliest."
Beaches in Mornington, Aspendale, Carrum, Seaford, Elwood, Werribee and Clifton Springs have been rated as having poor water quality on Saturday.
A full list of water quality reports for Victorian beaches can be found on the EPA's website.
"My main advice would be go to the swimming pool," Professor Taylor said.
