SCOTT MacGregor says being stung by a box jellyfish feels like "your skin is on fire".

Mr MacGregor was catching live bait with a cast net at the Proserpine River boat ramp on Conway Rd last weekend when he inadvertently caught a huge stinger.

"I actually got stung across my hands and on my back and across my legs," he said.

"It wasn't a bad sting but if I had the tentacles fully on me, it would have been a lot worse."

Mr MacGregor said he didn't require hospitalisation and treated the sting with vinegar at the scene.

But he described the pain of a jellyfish sting as "phenomenal".

"It feels like a fire sensation. I felt the pain for a good hour (and) when I got home I was itchy all night," he said.

On Facebook last weekend, Mr MacGregor posted a warning to online users of the Airlie Beach Buy Swap and Sell page.

"Hey girls and guys, I got this beauty of a box jelly today up the river but please don't swim or let your kids swim in the ocean or in closer as they are everywhere," he wrote.

"They are not just up the Proserpine River, they could be around the Port of Airlie boat ramps, Cannonvale Beach and the VMR boat ramp.

"They are pretty much everywhere."

The post on Facebook received 154 'likes' and 56 comments.

Mr MacGregor estimated the length of the box jellyfish's tentacles to be almost 2m long.

He said last weekend he saw more than 20 box jellyfish in the Proserpine River.

Mr MacGregor believed the box jellyfish he caught last weekend had come upriver to spawn in the mangroves.

Box jellyfish enter freshwater rivers to reproduce asexually in late summer and then die.

The jellyfish eggs, once fertilised, turn into tiny polyps that attach themselves to rocks, where they develop until the following spring.

A representative for the Mackay Base Hospital said in the past week, three patients had presented to the hospital with jellyfish stings and two people had been admitted to Proserpine Hospital in the same period.

If stung by box jellyfish, the advice is to apply normal vinegar and seek medical attention.