A giant, 23-tonne humpback whale took it upon itself to push an unsuspecting snorkeller through the water off the Cook Islands, looking to protect her from a nearby shark.

Stunning video and images show how the whale pushed whale biologist Nan Hauser with his head and his mouth, tucked her under its pectoral fin, and even lifted the biologist out of the water on one occasion.

Ms Hauser, 63, said the moment is perhaps proof of whale's intuitive nature to protect other species of animal - including humans - something she believes has never been captured on film. She also believes it is proof of the whale's intuition, a feeling she compared to firemen being willing to rush into a house on fire to help save the lives of those they do not know.

Lurking near the enormous mammal and Ms Hauser was a 4.5 metre tiger shark and though the animal is only visible in the distance in the footage, her team also filmed the diver from aboard a nearby boat, capturing her coming to the surface and shouting that there was a shark nearby.

Out of shot, another whale was persistently tail slapping and keeping the shark away from Ms Hauser and the whale that was pushing her.