Three children have been airlifted to hospital after receiving suspected Irukandji jellyfish stings on K'gari (Fraser Island).
One primary-school-aged girl was attended to by a rescue helicopter crew just after 10:30am on Tuesday after being stung on her chest while swimming in a creek near Wathumba beach.
She was flown with her father to Hervey Bay Hospital in a stable condition.
At 2:40pm, two sisters, aged five and seven, were also flown to Hervey Bay Hospital from Wathumba beach with suspected stings.
They are also in stable conditions.
The Queensland Ambulance Service describes Irukandji jellyfish as a small, extremely venomous species of box jellyfish, approximately two centimetres in diameter.
Their size can make them hard for swimmers to spot in the water.
They are most often found in tropical waters in Australia from November to May, and their stings can cause severe pain, vomiting, and breathing difficulties.
Lisa-ann Gershwin, director of the Australian Marine Stinger Advisory Service, said Irukandji stings are serious and deaths caused by them may be under-reported.
"There's two confirmed fatalities from Irukandji stings," she said.
"All of us that work with them, we all believe that there's been other fatalities that weren't confirmed to have an Irukandji underlying factor.
"The problem is there's nothing to test for in the blood, and there's no outward signs and signals of an Irukandji sting once the person has died."
Dr Gershwin said Irukandji jellyfish made yearly appearances on K'gari.
"Luckily, the season there doesn't tend to last very long compared with some other areas," she said.
"We might have a cluster of six one year, a cluster of 11 another year... over a period of days."
