All three Greenpeace protesters climbed down to police and were arrested

After nearly 10 hours of hanging on in strong winds, three Greenpeace protesters have come down from their perch high on the gantry of a Niwa research ship.

Police were waiting for them on the deck of the Tangaroa, which has been chartered by United States oil company Chevron to do survey work off the East Coast.

One by one, the protesters were led to a police van, after being verbally arrested earlier in the day.

MONIQUE FORD/FAIRFAX NZ Former Green Party co-leader Russel Norman speaks on the actions of the climate change protesters who boarded the Niwa ship.

Siana Fitzjohn, Kailas Wild and Adrian Sanders were cheered by fellow Greenpeace members on the dock, including former Greens co-leader Russel Norman, now executive director of Greenpeace in New Zealand.

Earlier on Tuesday, police climbed the ship's gantry twice in an effort to talk down the three protesters, but were rebuffed each time.

One protester was hanging from the gantry structure, one had climbed a mast, and another was attached to a ladder. They unfurled a banner proclaiming: "Climb it change".

KEVIN STENT/Stuff.co.nz Greenpeace activists stormed the Niwa research ship Tangaroa, claiming the vessel has been involved in oil exploration.

Police had already arrested two other protesters, Genevieve Toop and Niamh O'Flynn, who boarded the ship.

Greenpeace claimed the taxpayer-funded climate and ocean research ship had been refitted at a cost of $24 million for oil and gas exploration, and was preparing to leave Wellington for the East Coast.

But a Niwa spokeswoman said Tangaroa was not "searching" for oil. "We are a sea research vessel. We do have clients we work for on various things."

MONIQUE FORD/ FAIRFAX NZ The three Greenpeace protesters on the gantry of the Tangaroa research ship in Wellington Harbour.

Chevron confirmed on Tuesday that it had chartered the ship.

Science and Innovation Minister Steven Joyce said he did not know who the charterer was, but it "wouldn't suprise me at all" if it were an oil company.

Further, if an oil company did strike black gold, it would be a boon for New Zealand.

"The Tangaroa would just be doing surveying, but let's say it found oil or gas and they got an exploration licence, and if it turned into there being a production facility, there would be obvious benefits for New Zealand."

He pointed out earlier that the refit was completed back in 2010, and that Tangaroa had been doing survey work since the 1990s.

Any outrage about the fact a Niwa vessel was being used for oil and gas surveying would be "very conveniently recent", he said, because Niwa had been contracting commercially for 30 years.

"The ridiculous thing is, the vessel's research is being subsidised by the commercial work it does."

When accused on Twitter of not answering the question of whether Tangaroa had been surveying for oil, he tweeted "stop trolling ... you are boring".

Greenpeace climate campaigner Steve Abel said the Government was being dishonest.

"Right now, as John Key gets ready to head out to Paris for climate change talks, this taxpayer-funded science ship that should be doing vital environment work is trying to head out to survey our waters for the climate-wrecking oil industry."

Norman said it was liberating to be able to fight climate change at the "front line" in his new role.

He vowed he would take similar action at some point, but was not trained to do it yet.

"It's only my fourth week on the job and this is a specialist skill – I don't qualify. Maybe on another occasion."

Police said they had about six officers at the scene before the protesters came down. Their priority was to get the activists off the ship safely.

"We're engaging with them to find out what their end game is, and to see if there is a way to facilitate getting off the ship safely," Senior Sergeant Braydon Lenihan said.