Don't be alarmed by alien-like tentacles dangling off large bits of driftwood and ship wreckage - they are not harmful.

They are gooseneck barnacles, a common native marine species found around most of New Zealand.

There have been reports of their presence at Makorori Beach and Pouawa on the North Island's East Coast this week.

Photo / Gisborne Herald
Photo / Gisborne Herald

The barnacles gather on flotsam and jetsam (driftwood and ship wreckage) floating at sea and are generally seen only when the debris washes ashore.

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Department of Conservation marine technical advisor Clinton Duffy confirmed they were goose or gooseneck barnacles.

They are also found around the world in tropical and warm temperate waters.

"They are very common 'fouling organisms' on flotsam and jetsam," Duffy said.

"Within a matter of days the cyprid larvae, which lack a stalk, begin attaching to almost any object drifting at sea and they grow rapidly into the form seen here.

Photo / Gisborne Herald
Photo / Gisborne Herald

"It takes between 30 and 120 days to mature, depending on water temperature."

He believes they are the Lepas anatifera species, probably the most commonly seen around New Zealand.

A large piece of driftwood covered in gooseneck barnacles made international news last year after it washed up on Muriwai Beach.

It was dubbed the "Muriwai Monster" after an image of it was posted online and went viral.

Another species found in Portugal and Spain is considered a delicacy.

Its texture is described as similar to octopus or the neck of a soft-shell clam, with a strong sea-like, sweet taste.

Photo / Gisborne Herald
Photo / Gisborne Herald