The video shows the moment Hauser realizes there is a circling tiger shark nearby and she breaks the surface of the ocean to let her team know.
She said the encounter may be proof of a whale's intuitive nature to protect other species, including humans.
Biologist Nan Hauser swimming off the coast of Rarotonga, in the Cook Islands, when the giant creature swam in to prevent a "potentially deadly" attack.
The whale then shielded Nan underneath his pectoral fin and pushed her through the water to safety as another whale warded off the shark with its tail.
The encounter took place in October, but Hauser didn't upload the video until Monday. Throughout the video, you can see the whale tucking the snorkeler under his pectoral fin and pushing Hauser with his massive head.More news: Mafia op nabs 169 in Italy, Germany (2)
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James Sulikowski, a marine biologist and professor at the University of New England who has studied tiger sharks, admitted that Hauser had "an awesome experience". It's amusing how the tables are turned here: "I've spent the past 28 years protecting whales, and in the moment, I didn't even realize that they were protecting me!"
Hauser said she didn't understand the actions of the 25-ton whale that she met face-to-face in the Cook Islands. It seemed like hours. Once endangered, humpback whale numbers are now steadily increasing and most of these animals no longer need endangered species protections, NPR reported. "I was a bit bruised up", she said.
Hauser, president of the Center for Cetacean Research and Conservation, told the Portland Press Herald that whales are "altruistic" and often hide seals from predators, but she has never experienced or read about anything about a whale protecting a human.
Local fishermen described the tiger shark being as big "as a pickup truck". However, he said he was not convinced that the whale saved her life. "They truly display altruism - sometimes at the risk of losing their own lives", she says. Hauser says the team made a decision to abandon their drone footage because they didn't want to film her death. "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".