Dangers are emerging for swimmers at beaches, lakes and rivers after flooding and severe rain

Beaches, rivers and lakes across the country could feel the after-effects of continued heavy rainfall and dangerous flooding, placing swimmers in dangerous situations.

Surf Life Saving Australia national coastal safety manager Shane Daw said beach-goers could face several risks.

"People just need to be aware, during this time and shortly afterwards, around some of these waters that could be quite polluted," Mr Daw said.

"And that there's a risk of catching some sort of virus or bacteria as a result of the polluted waters."

As the major driver of pollution in recreational waters, rainfall generates storm water runoff and can trigger discharges from wastewater treatment systems.

Another major factor is hidden debris travelling into swimming waters.

"We know that there could be all sorts of debris, from furniture, through to cars and logs that can be moved around," Mr Daw said.

"They can become obstacles and potentially trap people."

Mr Daw also said flood waters reaching the coast could change particular environments people were familiar with.

"Banks that may have been there previously may have been eroded or washed away altogether and could be quite steep," he said.

"And where people thought it may have been a safe area previously, it could be quite deep."

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Sandbars may have shifted - altering currents - and hazards like rocks that were previously covered could now be exposed.

The NSW State of the Beaches report for 2021/22 showed a continued decline in water quality along the state's coastline as a result of consecutive rain-heavy years.

The latest report found that pollution levels for 20 per cent of 214 swimming sites, including beaches, estuaries, lakes and lagoons, were graded as fair, poor or very poor.

The number of sites, which includes Sydney's Coogee Beach, is up from 15 per cent in 2020/21 and 11 per cent in 2019/20 after the state's wettest summer in a decade

Royal Life Saving Society Australia national manager for research and policy Stacey Pidgeon said current weather events also placed greater risk on inland water bodies.

"A lot of those water bodies are often a lot higher than what they are usually," Ms Pidgeon said.

"That water can be running really fast and have strong currents in them."

Inland water bodies also had the added danger of being isolated and without lifesaver supervision.

"Often, since there's been so much rain and if it's really murky water, things may have shifted," Ms Pidgeon said.

"There could be trees or rocks or snags underneath the water that we just don't know about."

Rivers are the leading location for drownings in Australia, with 34 per cent of total drowning deaths in rivers and creeks linked to floods in the last financial year.

The 114 reported drowning deaths in river and creek locations in 2021/22 was a 48 per cent increase on the previous year.