Scientists are scratching their heads trying to find the source of a mysterious tidal surge that struck Papamoa Beach early Saturday knocking down fishermen and bringing in lines.

Fisherman Grahame Lindsey was out fishing the bottom of the tide at Karewa Parade during low tide at 5.30am on November 23 when he was stunned by the wave that powered up the beach.

Fisherman Grahame Lindsey was struck by a tidal surge at Papamoa Beach.

'It came up to nearly the high water mark,” says Grahame.

'It was low tide, it was about half past five and it brought the Kontiki in and laid the lines up the beach. It came in - it wasn't just a wave it was like a tsunami.

'It was quite frightening really. First time I have been fishing on the beach when that's happened. The tide came in and it stayed in for three or four minutes, then it just drained straight out like a huge vacuum cleaner. It was quite substantial.

'I don't know if anyone else saw it, but at that time of the morning there are not many people around anyway. But it was very mysterious.”

Another man fishing nearby saw the water rise from his ankles to waist deep, says Grahame.

'And my shirt was ripped. It threw the Kontiki right in. If there are waves out there and you have got a Kontiki, it will just pass and the Kontiki will stay there - but this brought the Kontiki right in. It's never happened like that before.”

About 9pm on Friday, November 22 there was an undersea earthquake between Fiji and Tonga that registered 6.6 on the Richter Scale.

The Pacific Tsunami Warning Centre in Hawaii did not put out a tsunami warning because the earthquake was 388km deep and none was thought likely. The eight hour travel time is about twice the time it took the Samoa tsunami to reach New Zealand in September 2009.

At that time on Saturday there was another earthquake closer to home, GeoNet reports.

At 5.25am Saturday there was a 2.9magnitude earthquake centred 70km east of Whangamata, but it was also deep seated, 213km, and it is unlikely anyone felt it.

Scientist Brad Scott, at GNS Science Wairakei, says there were some small earthquakes in the Kermadec Trench, but none big enough to create the surge spoken of.

People do from time to time report isolated surges that cannot be pinned to a particular cause, says Brad.

'We do get this sort of report every so often, made by normal straight-up people every year, or every other year,” says Brad.

Wayde Roest, at the Port of Tauranga hydrography department, says tide gauges at A Beacon and at the tug berth show ‘blips' of 100-200mm between 5.30am and 7.20am, but nothing like a surge of a magnitude big enough to bring the tide in for three or four minutes.

Today, Tauranga resident Rose Thomas contacted SunLive with news the wave originated from White Island, but again GNS Science can find no record of an earthquake big enough to generate a tsunami.

'There's been no public acknowledgement about what happened,” says Rose.

'I heard it was a metre high and if it had been at high tide it would have been disastrous,” says Rose.

'It wasn't even an eruption. That's my concern - they say things politically to try not to panic people. I think people want to know the truth. If it was a metre high at low tide, what would it have been like at high tide?”

GNS Scientist John Ristau says if it was a White Island earthquake it would have had to have been a sizeable one.

'In that case we would definitely know it had happened,” says seismologist at GNS Science John Ristau.

There was a 6.5 quake in Fiji, but that was Friday evening and would have been too early. It was also more than 200km deep and would not have generated a tsunami, says John.