The Fraser Island Association says there is not enough warnings for tourists, after five people suffered suspected irukandji jellyfish stings swimming near the island off south-east Queensland in the past week.
Last night, a 16-year-old boy was swimming off a yacht moored near Wathumba Creek on the western side of the island, when he was stung.
He was flown to the Hervey Bay hospital, as was a nine-year-old boy who was stung on Saturday.
There were three confirmed irukandji stings last week, including a five-year-old boy.
The three people were hospitalised last week after being stung while swimming on the western side of the island.
Fraser Island Association president David Anderson says people need to be extra cautiuos as there are no patrolled beaches.
"The western beach is where they have found the irukandji and where there have been recorded stings and it's not as well populated by tourists as the eastern beach," he said.
"The eastern beach is not a safe place to swim in.
"There are no flags, there are no lifesavers and the beach is dangerous because of the presence of rips and the presence often of sharks.
"At least if people are forewarned there is chance of irukandji stings, they can choose not to go in the water.
"If they do go in the water and they do have a sting, they need to know how to treat it."
Jellyfish are not the island's only natural hazard, after a 41-year-old man was bitten on the forehead by a centipede while he slept at Central Station early yesterday morning.
He was flown to the Hervey Bay Hospital in a stable condition.