Californian beachgoers were recently stunned by the sight of what appeared to be washed-up disembodied penises — and another similarly perplexing creature has been spotted on a South Australian beach.

Key points: A worm-like creature was recently spotted on an Eyre Peninsula beach

A worm-like creature was recently spotted on an Eyre Peninsula beach An invertebrate expert believes it was a species known as Sipunculus robustus

An invertebrate expert believes it was a species known as Sipunculus robustus While not uncommon, it has triggered associations with another, bigger event in California

ABC Eyre Peninsula radio presenter Emma Pedler was strolling along Louth Bay late last week when she spotted something unusual tangled in seaweed.

"The dog didn't see it — I'm glad I wasn't having to try and chase a dog up the beach with one of those in its mouth," she said.

"It was probably from my elbow to my wrist.

"These things just wash up on the beach and find themselves twirled in amongst the seaweed."

Pedler admitted she got "the giggles" after the find, but was even more surprised to see the news about a similar creature washing ashore in Northern California.

In that instance, a recent storm in Drakes Beach, north of San Francisco, uncovered a mass of worms from their burrows deep under the sand.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 44 seconds 44 s Thousands of so-called 'penis fish' recently washed up in California.

So, what is it?

The creatures, known as fat inkeeper worms or Urechis caupo, were soon labelled "penis fish" due to their phallic characteristics.

SA Museum marine invertebrate expert Shirley Sorokin said while the creatures on both beaches appeared similar, they were in fact quite different.

She said the one found at Louth Bay was most likely a worm-like invertebrate known as a Sipuncula "rather than a penis worm".

The creature has invited comparisons with California's fat inkeeper worms. ( ABC Eyre Peninsula: Emma Pedler )

"They do look similar and that Californian story was extraordinary," she said.

"The smaller Sipuncula are called 'peanut worms', but this is a large species.

"The one in [the] video looks like the species Sipunculus robustus, of which we have several specimens of in our collection."

Ms Sorokin said they were soft-bodied worm-like invertebrate that live in sand or mud and excavate burrows.

They are known to wash up after storms in South Australia's gulfs "and eat a variety of food from the mud including algae".

"They've got a mouth, so when they're in the mud they're taking in sand and the sand passes through their gut and they take tiny bits of organic matter out of the sand to digest," Ms Sorokin said.

"That netting-like look you can see on the outside of them is the muscles which just contract so they can push themselves through the sand."

There are more than 300 types throughout the world and can range in length from a few millimetres to half a metre.