Jellyfish experts say it is not exactly clear what is causing blooms of blue blubbers off the south-east Queensland coast.

The Queensland Museum has recently received reports of seas thick with blue blubbers off Coolum on the Sunshine Coast, north of Brisbane.

It was a similar sight to the blooms of the jellyfish spotted off Redcliffe late last year.

Queensland Museum scientist Dr Merrick Ekins said the exact cause of the jellyfish swarms was unknown, but there were a number of possibilities.

"It could be the result of overfishing, it could be a high nutrient load in the water, or it could just be the fact that the currents and the sea breezes are blowing them into a more confined area where people suddenly notice it," he said.

According to the Queensland Museum website, blue blubbers, or catostylus mosaicus, have a dome-shaped bell that can grow to 35 centimetres across.

They are the most common jellyfish in south-east Queensland.

Dr Ekins said despite all that was known about jellyfish, there was still an element of mystery about them.

"It just shows how little we know about lots of things in the ocean," he said.

"You could go out looking for jellyfish and you'd find new species, but we don't know a lot about them and their populations, and a lot of their biology is totally unknown to us."

Dr Ekins said while blue blubbers were not dangerous, "you can get stings from them, especially if you get it on soft skin like under your arms or your eyes".

"So you can get a sting from them but it should just be an irritation," he said.

"Just put cold packs or wrapped ice on them. But if you do get severely stung then do seek medical attention."