Marine biologist Nan Hauser feared she would be swallowed or crushed by a giant humpback whale — until she discovered it was trying to save her from a shark attack.

Ms Hauser said: “I was absolutely speechless that the whales had been protecting me from this huge tiger shark. I felt a deep love.

“I had heard about altruism in humpbacks with other species, and even read the scientific papers on it, but I never thought that they would show altruistic behaviour towards a human. I felt very privileged and grateful.”

The incident happened in the South Pacific Cook Islands last October, while Ms Hauser was working with Nature Conservation Films on a production about her work with whales.

Ms Hauser runs the Centre for Cetacean Research and Conservation in the Cook Islands, an independent British Commonwealth country.

Ms Hauser will talk about her rescue at the Bermuda Underwater Exploration Institute next Monday, starting at 7.30pm.

She will also discuss her 20 years of research on whales in the South Pacific and her work to protect them from threats. Ms Hauser was in the water when she spotted a 50-foot whale heading straight for her.

She said: “When he reached me he didn’t stop coming towards me.

“He kept swimming towards me and pushed me through the water until I was on his head and then his chin.

“I slid down his back, under his pectoral fin and off the end of his tail.

“He turned around quickly and I was back on his head again. He wouldn’t stop touching me for over 10 minutes and kept trying to tuck me underneath his flipper.

“He even lifted me out of the water at one point. I was watching him so intently that I didn’t see the huge shark very close by.

“I feared that if I stopped looking at him and protecting myself that I might get hit by him and it would break my bones.

“When I looked up for a moment, the shark was swimming right towards me.”

Ms Hauser said the tiger shark was between 15 and 18 feet long.

She added that, despite swimming with whales for about 28 years, she had no idea what the whale pushing her was trying to do until she saw the shark.

Ms Hauser said: “The whale could so easily have just turned his head quickly, hit me with his flipper or twisted his tail around and I would be dead.

“He would break my bones and rupture my organs in a matter of seconds.

“At one point, I was holding onto the very front of his face and he could have opened his mouth which is 16 feet across when fully open.

“So, I felt like I was in great danger. Then, when I saw the shark coming directly towards me I realised it was a giant tiger shark. It wasn’t until then that things started to make sense.”

• A film of the encounter can be seen here: https://www.youtube.com/watch?v=_NBjaUGaUos