An algal bloom that turned a number of Sydney beaches red this week has reached the Illawarra.
Thirroul Beach was initially closed but has now reopened.
The bloom can also be seen as a reddish streak in waters off Puckeys Beach, Wollongong’s Continental Baths and the lighthouse.
Wollongong City Council beach services co-ordinator Jason Foye said the bloom, which is spread out along the region's coastline, was being closely monitored.
"Luckily at North Beach it's scooting around the outside of the flagged area, but up north at Thirroul, we have had to shut Thirroul Beach because of it," he said.
"It has been out wide probably for the last couple of days, between one and two kilometres out to sea, there's been a large amount of red algae out there and the wind's started pushing it back to shore."
Mr Foye urged swimmers and surfers to avoid direct contact with the algae, and to get out of the water and wash thoroughly if they do find themselves in the bloom.
"It does irritate the skin and because of that we do shut the bathing areas down," he said.
Experts have identified the algae as Noctiluca scintillans also known as sea sparkle because it may appear to be phosphorescent at night.
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