New Zealanders are being warning to stay a safe distance from yellow-bellied sea snakes after one washed up on a Taranaki beach.

Photo: © Australian Museum / Hal Cogger

Lars Farrant, 10, spotted one of the venomous snakes just north of the Taranaki beach town of Oakura yesterday.

Photo: RNZ/ Robin Martin

Lars Farrant was walking the family dogs with his parents on the beach north of Oakura yesterday when the snake was pointed out to them.

"This guy came up to us and said there's a sea snake down there so we went to have a look and my mum got videos and pictures and then the tide came in and it swum away and poked its head up at one point."

The Year-6 student at Central School in New Plymouth said he was a bit nervous as he watched the reptile before it slithered away with the tide.

"I was feeling really scared, like, I got butterflies in my stomach, like hmmm, will it bite me?"

Lars said the snake which was grey on top and underneath, seemed a bit lethargic.

"It was just sitting there looking like it was getting a tan. It was like it was waiting for the tide to bring it back out to sea.

The pint-sized snake wrangler gave a speech to his home class, Room 11, about his exploits and his mum, Julie, had forwarded pictures and video to the school.

And the youngster now has a new nickname.

"Apparently I'm now called Snake Boy, according to my Mum."

Yellow-belly snakes unlikely to establish in NZ

Department of Conservation (DoC) senior marine ranger Callum Lilley said yellow-bellies were typically found in tropical waters but about 10 are sighted each year in New Zealand.

They are usually spotted around the east coast of the upper North Island but have been seen as far south as Cook Strait.

"[They are] pretty much a tropical species and they're not very good swimmers, so they're at the mercy of the currents and every so often they get pushed into New Zealand waters, but they won't really be able to establish here," Mr Lilley said.

Photo: SUPPLIED

Mr Lilley said yellow-bellies' venom could cause paralysis and cardiac arrest but they were difficult to provoke into an attack in colder climates.

He advised people to keep a safe distance from the snakes, to take photos and report any sighting to DoC.

The snakes are dark in colour on top and yellow underneath. The two colours usually meet abruptly to form a straight line along each side.

They measure up to 1m in length and their tails are compressed sideways to form a paddle, which is yellowish with large dark spots.