Mr Tallentire is calling for a new system to alert people in "real time" about water pollution after new information was uncovered through a parliamentary committee.
He said the State's rivers and oceans, including the Swan and Canning rivers, were polluted more than once a week between July 2011 and November 2014.
With the two rivers polluted by 21 reported sewage spills between July 1, 2011 and June 30, 2014, Mr Tallentire said swimmers were at risk of illnesses like gastroenteritis and ear and eye infections.
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READ NOW"Swimmers and other recreational users of our oceans and rivers need to be better informed of the health risks," he said.
"The current system is grossly inadequate and I think swimmers would be horrified if they actually knew what they were coming into contact with when they swim in our rivers and oceans."
Mr Tallentire said forcing swimmers to rely on signs was not good enough.
"It's clear that, at times, the amount of pollution in our rivers and oceans is at unacceptable levels," he said.
"It's made worse by the fact there is no system in place to warn people about the dangers."
However, a government spokeswoman said the State Government believed swimmers and other recreational users of oceans and rivers were well informed of health risks.
"The Department of Health issues media releases where appropriate. This is based on a risk management approach which considers many factors such as time of incident, potential exposure, type of contaminant, quantity of contaminant and weather conditions," the spokeswoman said.
"The Department of Health undertakes monitoring and reporting of recreational water quality in accordance with the national guidelines for managing recreational water."
The department also recommends people do not swim in rivers and estuaries for three days after rainfall above 10 millimetres.