Each mechanical shark sported rows of fearsome pointed teeth in its massive, wide-open mouth.

"The teeth were surprisingly accurate in Jaws considering it was a time when not many people had experienced these animals," according to Sophie Maycock, who studied sharks at the Netherlands' Leiden University, founded shark education website SharkSpeak, and co-wrote a book about them.

"The fact that they produced an animatronic shark with relatively accurate teeth is pretty good going."

But just how accurate is the rest of the science in Jaws?

And how has the blockbuster shaped shark policy today?

Can a shark even get that big?

The Jaws shark's biggest feature is, well, its size.

"That's a 20-footer," oceanographer Matt Hooper, played by Richard Dreyfuss, breathlessly says as he first spies the shark.

"Twenty-five, three tons of him," Robert Shaw as shark hunter Sam Quint responds.

That's 7.6 metres and 2.7 tonnes, or roughly as long and as heavy as a minibus.

But that seems unrealistic in real life, Ms Maycock says.

"There's not really a limit on their size apart from the fact that we've never seen great whites bigger really than six metres. So that is what scientific evidence we have of their maximum size."

Something that works against the feasibility of the Jaws shark's size is its sex, she adds.

"We would expect to see such a large individual being actually one of the girls, I'm afraid."

Female great whites tend to grow bigger than males. But the Jaws shark character is a bloke. He has male sex organs called "claspers".

In one scene, which uses actual footage of sharks in the wild, "you can see the claspers moving on his belly”, Ms Maycock says.

Shark attack behaviour

The first shark death in the movie is that of a young adult, Chrissy, who was swirled around the surface of the water before being pulled under.

But this is not realistic of a great white's hunting behaviour, according to Ms Maycock.

"They'll sneak up under their prey and wait till they're right beneath it and then they'll shoot vertically through the water to the surface to take their prey out," she says.

 Chrissy's attack in Jaws is much more tentative.

 "If this were real and a documentary, I might think that this shark was curious about her and just maybe mouthing at her to see what she is, but certainly not hunting," Ms Maycock says.

There's also a quote in the movie about sharks swallowing people whole, but this is inaccurate too.

Sharks eat large marine animals such as whales, dolphins and seals by ripping off and swallowing chunks.

"They've got multiple rows of teeth that can hook in, and their teeth are triangular in shape and serrated on both sides, so you've literally got a double-edged steak knife just cutting through."

The idea in the film that the shark in Jaws targets humans and becomes vindictive is "absurd", Ms Maycock says.

"These are human traits, not shark traits. Sharks don't hold a grudge or get annoyed."

And the audible shark "roars" in the film? They're yet another Hollywood invention, she says.

"It's a fantastic movie moment but no species of sharks has vocal cords. They do not roar, they do not growl. Cool as that would be, they don't."

Shark senses

In Jaws, police chief Martin Brody (played by Roy Scheider) reads a book that says sharks can pick up "erratic impulses" in the water.

This has truth to it. Ms Maycock suspects these "impulses" are the sort received by a shark when a struggling fish moves water around.

They can sense the water displacement through a strip of sensory cells along the sides of their body and head called lateral lines.

Sharks can detect electrical fields too, but only at very close range.

"Around their snout is lined with these specialised organs called ampullae of Lorenzini, which are jelly-filled pores that can sense electrical and magnetic fields," Ms Maycock says.

"So that means that when they're close to you they can actually feel your muscles contracting, feel your heart beating, so they can detect every movement you make in the water."

The aftermath of Jaws

Jaws was the biggest summer blockbuster of the time, bolstered by a $US 2 million marketing campaign, which was a massive ad-spend at the time.

Chris Pepin-Neff, a University of Sydney expert who studies shark attacks and public behaviour, says the campaign intended to terrify.

"It was specifically designed to have scary radio ads and really to reach into people's psyche and it worked really well."

As public perceptions around sharks shifted to fear, shark fishing tournaments sprang up around the US. Shark populations overall — not just great whites — plummeted.

In the years that followed, Peter Benchley, who wrote the novel Jaws, dedicated his life to shark conservation. Spielberg also said in multiple interviews that he regretted how his portrayal of a murderous rogue shark contributed to their decline.

In Australia, incidents involving sharks and people are today often met with a demand to kill the shark responsible.

After a trio of shark incidents during the early 2000s in WA and SA, Benchley wrote an open letter to the communities affected, Dr Pepin-Neff says.

"[It] says, 'Dear Australia, I invented rogue sharks. They do not exist. They do not intentionally try to kill us. This is nature and it's a risky environment and ... it's not a serial-killing shark from a movie.'"

Check out What the Duck?! presented by Dr Ann Jones to discover what else Hollywood got wrong in Jaws, and subscribe to the podcast for more.