Watch the shocking moment a 400 kilo dolphin crashes onto a boat in New Zealand

The trio of friends were fishing off the coast of Northland, New Zealand when the dolphin landed on their boat.

Dean Harrison, Milton Brookland and Austin Holbrow said the animal was like a 'tornado' in their tiny boat as it thrashed around.

“A 400kg dolphin falling out of the sky is going to leave more than just a bruise on the body,” Harrison said.

He added: “In the blink of an eye, there was a massive crash and boom, then a live 400kg dolphin filling the inside of our small open top boat going absolutely ballistic.”

The trio were forced to scramble to the edges of the boat, clinging to the sides, as their fishing gear was scattered.

Holbrow reportedly suffered a hairline fracture in his arm as he was pinned between the boat and the dolphin's tail.

“We stood out of the way with our jaws hanging at our feet trying to comprehend the situation.

“It took quite a while for the brain to catch up and process what was actually happening,” Harrison said.

They said they were worried their boat would sink under the weight of the animal, and that it would suffer in the beating sun.

On reflection, the trio wondered "how the hell" they survived the encounter.

Harrison said that they weren't fishing in their usual spots. If they weren't so spread out in the boat they would have been crushed by the animal.

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“We had no way of getting him off the boat so we were stuck with him,” Harrison said.

“We were like, we’re gonna look after you buddy and figure out what to do with you.”

They called the Maritime radio service, who put them in touch with the Department of Conservation. They told them to keep the porpoise cool and shaded.

The fast-thinking trio then covered the dolphin in towels and hosed it with water.

They were then instructed by the Department of Conservation to go to Waitangi boat ramp where staff could meet them.

The aquatic mammal was checked over by a specialist, who found it was a juvenile male bottlenose dolphin about 420kg - 450kg.

The animal was held with a few scratches, from the mental boat, but was otherwise unharmed.

A tractor and many volunteers were used to lift the porpoise back into the water.

They were fishing at Cape Brett when the frightening encounter occurred.

The friends were heading to deeper water, to try and catch Kingfish, in a spot busy with birds.