VISITORS to Palm Beach have been shocked to discover a mountain of cornflake seaweed washed up on the sand.

Strong northerly and easterly winds are behind the arrival of the thick seaweed, which has seen beachgoers wading thigh-deep through the pile.

Griffith University's Centre for Coastal Management Research Manager Darrell Strauss said it was a process known as "upwelling".

"It happens when we get strong north and west winds for a long period of time like we've had over the last few days," he said.

"The seaweed's been around for a while, people have been swimming in it in the surf zone.

"But to have it come on shore like that is usually deep water being brought forward as the surface water is blown offshore."

With high tides getting lower and lower over the next week the seaweed is expected to stay for some time, taking more than a month to decompose.

A runner had to be rescued by a passer-by after getting stuck in the seaweed on her morning run on Wednesday.

A dog and its owner were also seen struggling to get through the seaweed.

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Palm Beach local Brooke Colless, who often visits the beach with her kids, said it was "crazy" to see.

"It stretches the whole of Eleventh Ave down to Fifth Ave and it's a mountain," she said.

"The kids had some fun with it, it feels pretty gross to me but they were swimming in it.

"Sometimes you see a few cornflake in the water but we haven't seen anything like that in Palm Beach for quite a while."

But while it may be fun to jump in, Gold Coast lifesavers have warned people to be careful around the seaweed.

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Gold Coast Lifesaving Services Coordinator Nathan Fife urged Gold Coasters to take care.

"It actually has sea life in it, so just make sure you stay out of it or take a freshwater shower after you get out," he said.

"You don't know what's in it, what's been washed up. It could be fishing hooks, anything sharp, I'd be very careful.

"The seaweed attracts sea snakes, jellyfish and bluebottles."