Beachgoers were stunned by some unusual sand formations — dubbed 'poo sand' by many amused people — found on a beach in Queensland.
One man decided to get to the bottom of sandy mystery, posting several pictures to a Facebook page searching for answers.
"I know this might be easy for you guys to find out or just a commonly known thing," he wrote on the post alongside the strange pictures, saying they appeared on Black Beach in Mackay, Queensland.
"But I have to say I have no idea what it is," he admitted.
Amused followers were quick to point out what the piles of sand looked like.
"Clearly it's sand poo," one user declared.
"Beach spaghetti," someone else wrote, with another jokingly adding the noodle shape was "completely safe to eat".
"It looks like somebody put wet sand in a cake frosting piping bag and squeezed it out the tip to make cool designs with the sand," another observed.
"The beach just s**t itself, gross," someone else joked.
What are lugworms?
Although the sand mounds had an uncanny resemblance to a pile of poo, most users identified the weird sand construction as the result of lugworms, a type of marine worm.
Lugworms live around 20cm under the surface of the wet sand in J and U-shaped burrows, with their head pointing downwards and tails towards the surface,
According to the Natural History Museum website, the worms feed on micro-organisms and organic matter in the water. The type of sand formation points to the type of lugworm pictured to be a 'blow' lug, commonly found on the upper and mid of a beach.
Although people were joking about the 'beach poo' they weren't too far off — the 'poo' shaped sand is the result of indigestible material that had passed through the worm and is ejected from the back of the burrow via its tail. This worm poo forms the distinctive casts on the surface.
Fishermen sometimes use lugworms for bait, as they are found in large colonies and are easy to dig as they burrow close to the surface.
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