A Kiwi kayaker who is trying to become the first person to paddle solo from Australia to New Zealand in huge seas has been forced to fend off an attacking shark.

Former Rotorua kayaker Scott Donaldson has faced an aggressive shark in worsening weather conditions as he makes the roughly 2000km crossing.

He is currently half way between Australia and New Zealand, about 1000km to the east of Cape Reinga.

Donaldson's wife Sarah spoke with the adventurer briefly on Friday via satellite phone and said despite some rough weather he was in good spirits.

"He's been in the cab for two days riding out a storm in 5-6 metre swells. The boat hasn't rolled but its been on its side a lot. The currents are still in his favour, and he's pleased with how far he's gotten," Sarah Donaldson said.

As well as the rough sea conditions, Scott Donaldson had also had an encounter with an aggressive shark.

"He had a 2.5m shark chasing him the other day trying to bite the rudder.

"Scott would stop paddling and the shark backed off but then once he resumed paddling, the shark would chase him again. The rudder is intact thank goodness."

Though he sits halfway between the two countries, Donaldson more than likely still has at least another 1500km still to paddle.

South east current and winds will carry him toward New Plymouth and the Taranaki Coast.

That's where Donaldson had to be rescued from in his 2014 crossing attempt which finished after 84 days.

Donaldson had been paddling half the Tasman with an unrepairable rudder, sitting out a once in 40-year storm, and looking at Mount Taranaki 80km off the coast of New Zealand before protocol dictated it unsafe to continue.

Team leader Nigel Escott said today he was pleased with Donaldson's northerly position at present which boded well for the rest of the trip.

"The progress so far has been about getting into the right position to utilise the south east current. In the next few days we'll see him veer to the right and start heading south," Escott said.

"We've been utilising Scott's physical strength thus far to get through this tough bit of weather. Even with the bad weather he's experienced, he'll still be able to paddle around 90km in the last three days."

With his trans-Tasman kayak attempt, Donaldson is raising awareness about asthma, a condition he suffers from. Donations can be made via Givealittle.

Follow Scott Donaldson's progress via tasmankayak.com