Two people have been stung by stonefish at popular swimming spots on Queensland's Gold and Sunshine coasts, bringing the number injured by the venomous fish in the state's south-east to four people in just over a week.
A 27-year-old man had been wading in waist-deep water outside the flags at Caloundra's Bulcock Beach on Friday when he was stung by the potentially deadly rock-like fish.
Lifeguards treated the man, who was then taken to the Sunshine Coast University Hospital.
Meanwhile, lifeguards removed a stonefish barb from a 35-year-old woman who was stung at Tallebudgera Creek on the Gold Coast.
Two children have also been injured by the stonefish at the same section of the popular Tallebudgera swimming spot over the past eight days.
Stonefish are among the most venomous of all fish species and can be found in shallow coastal waters along the Australian coastline.
An expert in treating fish stings, Dr Simon Jensen from Sunshine Coast University Hospital said the stonefish injuries were the latest in a string of cases this summer.
He said 10 people on the Sunshine Coast had been treated this month for venomous fish stings, mostly from stonefish.
"It's not uncommon for people to come out of the water screaming in pain," Dr Jensen said.
"People describe it as the worst pain they've ever had and it certainly doesn't respond particularly well to normal painkillers."
He said the pain could spread from the a foot injury right up the leg, and there could be more serious side-effects.
"As well as pain, we occasionally see cardiac effects, low blood pressure, [patients] can be delirious, nauseated," he said.
Dr Jensen said people should take particular care around rockpools with sandy bottoms, the favoured habitat for stonefish, which can survive 24 hours out of water.
Associate Professor Jamie Seymour, from the Australian Institute of Tropical Medicine in far north Queensland, said swimmers should avoid planting their feet on the ground in rocky areas.
"Stonefish have got 13 spines along its back, just like a normal fish, and with each of those spines there are two associated venom sacks," he said.
"[When] you stand on that spine and it goes into your foot ... what happens is you press those venom sacks and venom comes out of the spine."
Mr Seymour said without medical attention, the effect of the venom could be deadly.
"There have been a few recorded cases throughout the world where people have died from stonefish, so it [stonefish stings effects] can be from mild pain, through to death."
'Stonefish sit there waiting'
Queensland Museum fish expert Jeff Johnson said it was not surprising for stings to occur at Tallebudgera Creek.
"Around the mouths of creeks, estuaries, rivers, that's good stonefish habitat because the tide comes in and out, it brings food for the stonefish," he said.
"There's lots of small fish and prawns and things moving in and out with the tide.
"The stonefish sits there semi-buried at the bottom waiting for one to come along and make a feed from it."
Gold Coast Surf Life Saving coordinator Nathan Fife said the recent spate of stonefish stings at Tallebudgera was unusual.
"We haven't seen many of them, so having three in a week and a half is why we want to put a warning out for people to be careful," he said.
Lifesavers have told swimmers to be wary around rocks and have advised people to stick to sandy areas where stonefish do not inhabit.
Mr Fife said anyone who gets stung by a stone fish should not ignore the pain.
"Get medical attention straight away, because the sting can get pretty bad once the venom gets into you," he said.