THERE are two box jellyfish populations in Gladstone and so swimmers need to be cautious this summer, Dr Lisa-Ann Gershwin has warned.
"Box jellyfish live and breed near Turkey Beach and in the Calliope River. They don't just get washed to Gladstone from up north," said Dr Gershwin from the Australian Marine Stinger Advisory Services.
She said even though sightings of the deadly animals were rare, it only takes one to kill you.
"Jellyfish can be anywhere in the water and dragging nets is good practice, but isn't enough to confirm there are none at all," she said.
"People have died in Gladstone from box jellyfish and more people will, if we aren't careful."
Dr Gershwin said keeping safe in summer is easy - just wear protective clothing.
"It's about how much skin comes into contact with the venomous tentacles," she said.
"Research tells us that if you are stung on the hands or feet only, there is not enough surface area for the venom to kill you.
"It will be incredibly painful, but not fatal."
If you cover your arms, legs and torso and keep your face out of the water, it dramatically decreases the chance of death.
"Most people that aren't protected die within 2-4 minutes," she said.