In 1975, a man watched a movie. The movie was called Jaws and the man was one Mr Fidel Castro. The Cuban leader liked what he saw and would reportedly go on to proclaim it one of the greatest American films of all time. The chances are you feel the same, but Fidel saw something in Jaws that perhaps you don't.

For him, this iconic tale of a small town with a big, fishy problem is a Marxist critique of Capitalist oppression, and its hero isn't Roy Scheider's embattled everyman, Police Chief Martin Brody, but the shark - a valiant crusader who takes justified revenge on a bourgeois and excessive American elite.

Castro's unique take serves to show just how popular, thought-provoking and misunderstood Jaws was and still is. Since its release, Steven Spielberg's landmark blockbuster has attracted thousands of pages of analysis, each one seeking to unlock the mysteries of a film that struck a nerve in the summer of '75 and went on to smash box-office records.

Depending on who you read, Jaws is a misogynist tract that revels in the opening sequence death of the sexually-liberated Chrissie Watkins; a psychosexual thriller with a distinctly phallic antagonist; a middle-class manifesto (sorry Fidel) that only resolves itself when Robert Shaw's working schmoe Quint perishes, or a Watergate dissection that vilifies a corrupt mayor not a thousand leagues away from Richard Nixon. Take your pick, there's plenty to choose from...

All such readings have value, but only one captures the true secret of Jaws' unexpected success and long-lasting popularity. Writing about the most influential films of all time in the Telegraph last year, Mark Cousins argued that Jaws created a culture of 'want see' - in other words, it gave filmgoers the chance to witness the kind of spectacular sights they wanted to see in real life, but couldn't outside of the cinema.

This primal urge was exploited in the film's revolutionary promotional campaign, which cost over $1.8 million to create and prominently featured the iconic image of a shark surging upwards through the water towards a helpless female swimmer. Revealing so little, but suggesting so much, this single image was a masterpiece of movie marketing, not just selling a film, but an emotion. Something, somewhere, is out to get you.

Ever the crowd-pleaser, Spielberg repeatedly delivers on that emotion in the film proper. The opening sequence (which inspired the poster), sees young swimmer Chrissie Watkins get torn beneath the ocean surface by our fishy menace. Cutting from the shark's POV to shots of an oblivious and helpless Chrissie, Spielberg provides an electrifying thrill ride that forces us to jolt from one extreme to the other, making us both victim and attacker.

Later, we become passive observer as he puts us in the place of Scheider's thalassophobic Brody during the build-up to the attack on young Alex Kintner. Spielberg's camera twitches anxiously across the beach just as Brody's eyes do, watching and waiting for the disaster we know lays in wait. When it does come, Spielberg's famous dolly zoom makes explicitly visual the sequence's underlying fear and confirms our intense relationship with the film. We're not just watching Jaws; we're living it.

Such a visceral approach was by no means rare in the 70s, a period characterised by gritty police dramas, paranoid conspiracy thrillers and violent gangster epics, but Jaws' common touch was. Aided by Carl Gottlieb's smart script and Scheider's sensitive performance, Spielberg's Brody is a flawed everyman struggling to conquer the shark, his fear of the water and Amity's corrupt mayor. These are more grounded threats than those faced by many other 70s leads, and the fact that Brody emerges from all three as a stronger man makes the film a deeply relateable piece of escapism, as well as an intense ride. This is 'want to be' film-making as much as 'want to see' film-making.

Nearly 40 years on, Jaws is being re-issued in a climate similar to the one it debuted in. Politicians are still corrupt, the year's big releases are still dark, moody and morally ambiguous, and audiences are still searching for visceral cinematic kicks.

The only difference now is that those kicks are more difficult to find. Cinema's obsession with the methods of film-making - 3D, high-definition, digital projection - is beginning to conceal the message. Building an imaginary barrier between the audience and the movie itself, Hollywood is forever reminding us that this shimmering, crystal clear, 'immersive' piece of entertainment isn't real. That film you're watching really is just a film.

Still razor-sharp and scenting blood, Jaws is anything but.