UPDATED 4.45pm: Police are continuing to negotiate with Greenpeace protestors on the Tangaroa.

Three protestors have climbed up the gantry on the NIWA vessel, and are resisting efforts from police to talk them down.

The Tangaroa is a NIWA taxpayer-funded climate and ocean research boat

The protestors have locked themselves atop the ship in Wellington Harbour - protesting the fact it's been used to survey for oil.

Two other protestors were arrested earlier.

Greenpeace campaigner Steve Abel said police have climbed up to them six or seven times now, but he's not sure what they're saying.

He said the activists will stay up there as long as they can, and said the health and safety of the climbers is paramount.

Abel claims the ship is surveying for oil on the East Coast on behalf of petroleum giants Statoil and Chevron.

"We believe it is great hypocrisy on the part of the government. In the week before the climate summit in Paris this vessel is looking for oil - the exact oil that we can't afford to burn if we're going to avoid climate change."

Mr Abel said at the moment the climbers are happy and comfortable, and resolute in their protest of the boat carrying out oil surveying on the East Coast.

Police have been seen twice approaching one of the protestors, apparently talking to them, then retreating back down to the deck.

NIWA's chief executive John Morgan has expressed his disappointment and concern that the trespassers breached security, and safety measures, to board the vessel.

John Morgan said the organisation takes health and safety extremely seriously.

He said while it's tolerant of minority views, trespassers putting themselves and others at risk is a matter for Police to deal with.

He said NIWA vessels undertake a wide range of activities, including ocean geology, minerals and petroleum research.