Ever since the biblical tale of Jonah and the whale, humans have been fascinated by the idea of surviving inside one of the ocean's largest creatures.

The film Whalefall, released today, has revived that enduring fear.

It tells the story of a scuba diver who is swallowed by a sperm whale and given just one hour to escape before his oxygen runs out.

But could such a nightmare ever happen in real life?

The answer, according to marine scientists, is surprisingly complicated.

While being swallowed by most whale species is physically impossible, experts say there is one giant exception – the sperm whale, that features in the film.

These enormous creatures reach lengths of up to 60ft (18m) and feed on large prey including giant squid, making them one of the few whale species with a throat wide enough to accommodate a human.

Joy Reidenberg, a comparative anatomist at the Icahn School of Medicine at Mount Sinai, worked as a consultant on Whalefall.

She explained that for all but one species, swallowing a human is physically impossible.

Speaking to Science News, she explained that a 'very big adult sperm whale' could do it, but that it would take a full-grown male at the very top end of the scale – 'bigger than most of the ones that we're used to seeing'.

Other whales, however, simply could not manage it.

There was a famous case in 2021 when a Massachusetts lobster diver, called Michael Packard, was briefly trapped inside a humpback whale's mouth.

But although humpbacks have mouths large enough to engulf a person, their throats are not.

'A humpback's throat is roughly the size of a human fist,' Nicola Hodgins, from Whale and Dolphin Conservation, told National Geographic.

As a result, the man was likely 'engulfed as opposed to swallowed' before the whale realised its mistake and spat him out.

Even if a person were swallowed, surviving inside the whale would be an entirely different matter.

Sperm whales normally prey on squid, including giant squid, and scientists believe they suck prey into their mouths by creating powerful low pressure in the throat before swallowing it whole.

The first challenge, if swallowed, would be oxygen.

In Whalefall, the diver survives using the dwindling supply of air in his scuba tank. While that might buy valuable time, experts say conditions inside the whale would still be extremely hostile.

The stomach would be dark, wet, cramped and filled with digestive fluids. There would also be little or no breathable air once a diver's tank was exhausted.

Increasing pressure, meanwhile, presents another obstacle.

As sperm whales hunt for squid in the deep ocean, they routinely dive to depths that would be fatal to an unprotected human.

While a diver inside the whale might be spared direct contact with the surrounding water, the immense forces involved could still create a highly hazardous environment.

Even if someone survived the descent into the deep sea, they would eventually have to contend with the whale's digestive system.

The sperm whale's stomach is not a giant hollow cave, as often portrayed in fiction.

Instead, it consists of several compartments that help break down tough prey such as squid, including species armed with sharp beaks and tentacles.

Any human trapped inside would face not only suffocation but also heat, digestive fluids and constant movement as the whale swam and dived through the ocean.