The Eurobodalla Shire Council has advised residents and visitors that all beaches in shire are closed for swimming.
A council spokesperson said fire debris washed into waterways from recent heavy rain has resulted in dangerous conditions and poor water quality.
"Some beaches may have been affected by sewer overflows, and these have been signposted," the spokesperson said.
"Many of Eurobodalla's rivers, bays and beaches are covered with burnt twigs and branches, timber, and a fair amount of litter.
"This is true for the entire southern NSW coastline."
The Eurobodalla Shire Council and the NSW Government undertake regular monitoring and sampling of water quality and the community will be notified when conditions have improved.
The spokesperson said swimming is not recommended while the water remains dirty.
"The debris will continue to accumulate but, over time, nature will take its course and Eurobodalla's waterways and 143 kilometres of coastline will be cleansed of organic matter.," the spokesperson said.
"Anyone finding litter and rubbish, particularly plastic, can assist by collecting it for disposal."
Any risks to public safety can be reported to Council on 4474 1000.
Recording collected litter in the Australian Marine Debris Database provides researchers and lawmakers the information they need to work toward stopping litter at the source, to the benefit of marine wildlife.
The database is hosted by the Tangaroa Blue Foundation, with a simple-to-use downloadable phone app. To find out more, CLICK HERE.