A snorkeller is in hospital after the ninth suspected irukandji jellyfish sting at Queensland's Fraser Island in under a week.
The 19-year-old man was stung on the lip while swimming in Coongul Creek on the western side of the island about 11am on Tuesday.
He was treated at the scene by paramedics before being airlifted to Bundaberg Base Hospital.
Paramedic Phillip Switzer said the man didn't see the jellyfish but experienced severe nausea, vomiting and pain within 10 minutes of being stung.
The incident is the ninth suspected irukandji sting at Fraser Island since Wednesday, with the venomous jellyfish positively identified as being responsible for at least one of the incidents.
Mr Switzer said all nine cases had happened on the western side of the island in its calmer and warmer waters.
"We have no evidence to say they are or are not irukandji," Mr Switzer said.
"There are certainly jellyfish floating but no one's actually caught one so we can't disprove that they're not irukandji or a jellyfish in the same family that produced the symptoms of an irukandji jellyfish."
Eight people people were treated at Fraser Island for irukandji-like symptoms in 2015, Mr Switzer said.
The irukandji - the world's smallest and most venomous box jellyfish - is usually found in waters north of Mackay, about 700km further up the coast.
Victims initially experience severe nausea, followed by multiple bouts of vomiting, pain that normally begins in the back and radiates up the neck to the chest and abdominal cavity, leg pain and cramping.
There is an unusual psychological effect too: victims report experiencing an acute sense of impending doom.
Mr Switzer said anyone believed to have been stung by one should treat the sting with vinegar and call triple zero.
AAP