JELLYFISH are stalking Fraser Coast beaches in plague-like proportions and surf lifesavers are warning swimmers to be careful.
Catostylus jellyfish, also known as blue blubber jellyfish, have been turning up in "abnormally high" numbers, according to Craig Holden, Surf Life Saving Queensland's regional manager for the Wide Bay Capricornia.
But while the species was not deadly, Mr Holden said swimmers, particularly parents with young children, still had to be vigilant.
"The sting can cause a minor irritation and people certainly need to be aware that they are there," he said.
"People tend to see the size of them and panic, but it is nothing for people to be alarmed about."
Mr Holden said some people would not even feel the sting of a blubber jellyfish, but others might receive some minor pain.
He urged anyone who was stung to see their local surf lifesavers, who are trained to treat jellyfish stings.
Alternatively, warm water or ice could help ease the pain.
Blue blubber jellyfish, which grow to about 35cm in diameter, have peppered the sand of Hervey Bay's beaches for weeks and large numbers have also been spotted up at Bundaberg. But local lifeguards have only treated a handful of beachgoers for stings so far this season, Mr Holden said.
Box jellyfish and irukandji were the deadly varieties, but Mr Holden said they were uncommon in Fraser Coast waters and were more likely to be found in north Queensland.