FIVE teenagers were stung by the dangerous Moreton Bay stinger, also known as "the fire jelly", at the Sunshine Coast Surf Life Saving branch championships at Bribie Island on Saturday.
Two were sent to Caboolture Hospital for observation but were discharged later in the day.
The box-shaped jellyfish has an extremely painful sting and has been known in rare cases to cause an "Irukandji-type" syndrome.
These symptoms include muscle pains, painful breathing and anxiety. It is not known to be deadly.
Sunshine Coast Surf Lifesaving service co-ordinator Aaron Purchase said the championships were put on hold after four competitors were stung at the same time.
"Two were taken to Caboolture Hospital as they were in quite severe pain," he said.
Mr Purchase said organisers searched the area with an IRB the next day and did not see any more stingers.
The event continued without incident.
Mr Purchase could not confirm which clubs the teenagers were from, but said they were all about 15 or 16 years old.
He said conditions were not anything out of the ordinary before the event.
Marine stingers expert Peter Fenner said it was very unlikely the jellyfish would have been visible from an IRB.
"They don't float on the surface and they are transparent, you would have to be trained to see them," Dr Fenner said.
He said stingers were fairly common in the Moreton Bay region.
"Usually they're very painful and that's it," he said.
Lisa-Ann Gershwin, from the Australian Marine Stingers Advisory Service, said the species was considered high risk.
Dr Gershwin is hoping to collect more data on stingers.
"We are a group of researchers who hope to manage the jellyfish problem in an accurate, balanced way so people can have more fun at the beach," she said.
"We are a developing a predictive system of Irukandji so we can know when they are likely to be in the water."
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