Department of Conservation ranger Jamie Quirk said the sighting was a rare occurrence.
"It is not normal but not impossible. The water temperatures are still really warm and every 15 to 20 years we get sea snakes washing up on our shores.
"They are usually at Te Araroa and the East Cape. We have not seen them much closer than that," Mr Quirk said. "Definitely leave them alone. Their bite is extremely poisonous."
The Ministry of Primary Industries was called and identified the snake as a yellow-bellied sea snake. It reiterated they were venomous and should be left alone.
The snake disappeared with the high tide.