Humpback whales have been documented warding off predators from their offspring. Protecting a human? Now that's a first.

A never-before-captured video shows the incredible moment a 22,000-kilogram (48,500-pound) humpback whale appears to rescue a snorkeler from a nearby tiger shark.

Filmed in the warm seas off the Cook Islands, the video shows a large whale pushing Nan Hauser to the surface using its head and mouth. The 63-year-old marine biologist was then tucked under the whale's pectoral fin, which, she later realized, likely shielded her from a nearby tiger shark.

A second whale then uses its tail, slapping it through the water to keep the shark away.

Reaching up to 19 meters (62 feet) in length, humpback whales are relative to a bus in size. It's no wonder Hauser was left bruised by the encounter and said it felt like hours.

"I have 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," Hauser, president and director of the Center for Cetacean Research and Conservation, told the Independent.

When the whale began pushing Hauser around, her research team on a nearby vessel feared for her life and abandoned their drone footage because, as Hauser described, they "did not want to film my death."

It's not the first time the ocean giant has been observed protecting a defenseless species. In a 2009 research trip to Antarctica, marine researcher Robert Pitman recorded a pair of humpback whales protecting an isolated seal on an ice floe from a pod of killer whales. Inspired by his observation, Pittman later went on to explore the seemingly altruistic behavior exhibited by humpback whales. His research analyzed more than 100 interactions between humpback and killer whales around the world from 1951-2012.

But protecting a human? That's a first, according to Hauser, who notes this is the first documented case where a humpback whale has protected a human from a tiger shark. She believes this is further proof of whales' instinct to protect other species and hopes the footage will help spur further research.