Video of what is believed to be a sea snake that has washed up on a Taranaki beach.

A venomous snake that washed ashore in Taranaki is apparently a New Zealand native species that used to be killed on sight.

On Sunday, 10-year-old Lars Farrant found a snake on Tapuae Estate Beach, just south of New Plymouth, and after some research concluded it was a yellow-bellied sea snake.

Nicola Nelson, associate professor at Victoria University's school of biological sciences in Wellington, said while it usually found closer to the tropics, that species was classed as a native animal of New Zealand.

Lars Farrant Lars Farrant found the snake, which is classed as a native, on a beach in Taranaki.

Nelson, who is also the president of the Society for Research on Amphibians and Reptiles in New Zealand, said people had been finding them on the beach for decades but usually killed them.

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That had since changed as people became more educated about them, she said.

Lars Farrant The snakes scientific name is Pelamis platurus, which means flat-tailed.

National Institute of Water and Atmosphere principal scientist Malcom Francis said the snake could have followed the currents down from the Manukau Harbour and succumbed to the region's colder water before washing ashore.

The water temperature around Taranaki had averaged around 18C over the last four days, which was warm for this time of year but would be cold compared to the snake's home in the tropics.

Department of Conservation (DOC) senior ranger marine, Callum Lilley, said three snakes washed ashore in Taranaki in 2009.

A yellow bellied sea snake pictured on a beach in Costa Rica.

Lilley said he had only seen a video of the snake but it appeared Lars was correct with his identification.

The yellow-bellied sea snake is a distant relative of the cobra and can inject venom through its small fangs, causing paralysis, severe pain and, in severe cases, cardiac arrest and death.

However there have been no deaths reported from the snake in Australia or New Zealand.

Yellow-bellied and sea kraits were the only snakes that visited New Zealand and kraits were only found further north, Lilley said.

"Around New Zealand, because they're a tropical species we would get about three sightings a year," he said.

"They're not very good swimmers so they're largely at the mercy of the currents," he said.

Despite their venom, they were unlikely to attack unless provoked as they were "not a very aggressive species".

If anyone came across one, Lilley encouraged them to stay at a safe distance, get a photo of it and report the sighting to DOC.

The snakes can be identified by dark colouring on the upper half of the body and the yellowish colour on the lower half.

Its scientific name is Pelamis platurus, which means flat-tailed.

It's not the first time a slithering creature has caused a stir in Taranaki.

In 2004, two boys caught what they thought was a sea snake while fishing in Port Taranaki.

They kept it in a bucket but released it before it could be properly identified.

At the time, the Ministry of Fisheries said it was likely to be a yellow-bellied sea snake, while Te Papa said it was probably a long-finned worm eel or a snake eel, both of which are harmless.

In 2010 New Plymouth man Andy Griffin found what he believed was a snake near Awakino.

However, Te Papa identified it as a short-finned worm eel, which lives in the sediments on the sea floor.