This is the breathtaking moment a colossal 50,000-pound humpback whale shielded an oblivious snorkeller from a SHARK by guiding her through the water.
The remarkable footage captured by Nan Hauser and her team - including point-of-view shots - reveals how the whale nudged marine biologist Nan using its head and mouth.
The male tucked her beneath its pectoral fin - and even hoisted the biologist out of the water on one occasion - though this cannot be seen in the footage.
Nan believes this demonstrates the whale's instinctive nature to protect other species - including humans - something she reckons has never been documented on film before.
It's an instinct the biologist likens to firefighters being prepared to dash into a burning building to rescue the lives of complete strangers.
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Lurking nearby the roughly-50,000-pound creature and Nan was a 15-foot tiger shark, Nan said, and whilst the predator is only visible in the distance in the footage, Nan's team also recorded the diver from a nearby vessel.
That footage shows her surfacing and yelling that there was a shark in the vicinity.
Beyond the frame, another whale was repeatedly tail slapping and driving the shark away from Nan and the whale that was guiding her.
When Nan eventually spotted the shark she initially assumed it was another whale - until she saw its tail swaying from side to side rather than up and down, like a whale.
As Nan made it back to the vessel's safety, in the waters near Muri Beach, Rarotonga, the Cook Islands, in October, the whale even came up to the surface to monitor her wellbeing.
Nan, a Cook Islands resident, explained: "I wasn't sure what the whale was up to when he approached me, and it didn't stop pushing me around for over 10 minutes. It seemed like hours. I was a bit bruised up.
"I've spent 28 years underwater with whales, and have never had a whale so tactile and so insistent on putting me on his head, or belly, or back, or, most of all, trying to tuck me under his huge pectoral fin.
"I tried to get away from him for fear that if he rammed me too hard, or hit me with his flippers or tail, that would break my bones and rupture my organs. If he held me under his pectoral fin, I would have drowned.
"I didn't want to panic, because I knew that he would pick up on my fear.
"I stayed calm to a point but was sure that it was most likely going to be a deadly encounter.
"I feel a very close kinship with animals, so despite my trepidation, I tried to stay calm and figure out how to get away from him.
"I never took my eyes off him which is why I didn't see the shark right away."
While the clip shows the whale biologist touching the enormous creature - something that shouldn't be promoted - she insisted the whale was the one forcefully initiating direct physical contact with her.
Nan said: "I never touch the whales that I study unless they are sick or stranded on the beach.
"In my head, I was a bit amused since I write Rules and Regulations about whale harassment - and here I was being harassed by a whale".
Nan had never encountered the whale before diving into the water that day.
The cameraman who captured the incident close by had never filmed whales previously, so was oblivious to just how extraordinary this behaviour was.
On Nan's nearby research vessel, however, her colleagues were worried for her safety, abandoning their drone footage because, as Nan recalls the moment, they "did not want to film my death."
Nan had heard of the altruistic behavior of humpback whales before - protecting their young, other species of whales, seals, and dolphins - but scientists have never seen humpbacks actually protecting humans.
Dolphins have been known to exhibit protective behavior and many stories have been told.
Nan had never witnessed such an incident firsthand with a humpback, or seen footage in the past 28 years of studying whales.
For over 10 minutes, Nan said, she was focused on the whale, unaware of the shark nearby.
The biologist now hopes to share the footage that she and her colleagues were able to capture, in order to expand research and awareness of such actions from whales.
Nan said: "There is a published scientific paper about humpbacks protecting other species of animals, by Robert Pitman.
"For instance, they hide seals under their pectoral fins to protect them from killer whales.
"They truly display altruism - sometimes at the risk of losing their own lives."
This marks the first recorded instance where a humpback whale has shielded a human from a massive tiger shark, according to Nan.
"Other fishermen and divers have spotted this same shark near the reef and claim that it's as large as a pickup truck.
"Some estimate that it is 20 feet long.
"It's amusing how the roles are reversed here: I've dedicated the last 28 years to protecting whales, and in that moment, I didn't even realise they were protecting me!".
