If Jaws were released today, rather than 40 years ago, it’d be greeted as a mid-budget creature feature, a small-town drama centered around three relatable characters. There’s action, yes, and suspense, and some shocking gore. But it bears little resemblance to the blockbuster culture it’s credited for creating: Steven Spielberg’s film was given a near-unprecedented “wide” release, opening on 409 screens when it hit cinemas on June 20, 1975. Last weekend, Jurassic World debuted on 4,274. Jaws might be the primordial ooze from which Hollywood’s modern-day strategies emerged, but to look back on it now, it’s almost disarmingly quaint.

Jaws’s strengths and weaknesses have been dissected at length in the years since its release. Only Spielberg’s third feature-length film at the time, the adaptation of Peter Benchley’s hit novel about a man-eating shark went almost three times over budget and featured a mechanical prop that looked the furthest thing from terrifying. To combat that, Spielberg mostly shot around it, building tension through underwater point-of-view footage and John Williams’ landmark, minimalist score. Rolled out nationwide with the kind of blitzkrieg advertising and promotional tie-ins that would later become Hollywood norms, Jaws is the prototype of the modern blockbuster, and was the highest-grossing film of all time until Star Wars came out two years later. If there’s anything you love or hate about the big-budget, studio action movie, it can probably be traced back to Jaws. And yet what makes the film work is not the history-making blueprint it set out, but instead all of the charming, unsung idiosyncrasies that make it a great film.

Spielberg’s first stroke of genius was in the casting—the director shied away from booking any A-list stars, knowing their screen presence might overpower the picture (Charlton Heston was among those interested in the script, but was turned down). Roy Scheider was probably the biggest name, coming off The French Connection, as Amity’s flustered police chief, Brody; Robert Shaw, as shark hunter Quint, was a well-regarded British character actor who usually played villains, and Richard Dreyfuss, as marine biologist Matt Hooper, was best known for his role in George Lucas’ American Graffiti.

Jaws is hardly a high-stakes, apocalyptic tale; the central conflict has a more intimate, claustrophobic feel. In the film, Amity’s shark attacks are claiming lives in the single digits, not the thousands, and they’re occurring on a single tourist-clogged beach, not the whole planet. The three men who take it upon themselves to destroying the beast are hardly the best at what they do—Quint is a washed-up fisherman, Brody a seaside cop who’s afraid of the water, and Hooper’s an agreeable nerd who’s just as excited to photograph the shark as he is to kill it. Spielberg spoke of wanting to make the film feel like it could happen to anyone, and that approach helped soften the blow of Jaws’s disappointing technical effects. The shark is a powerful beast, but once it emerges from the water, it almost looks as hapless as the people around it, flailing around on Quint’s boat in a failed effort to sink it.

Spielberg’s grounded, everyman approach to heroism was one he would repeat throughout his career. Jurassic Park doesn’t feature any superstars, nor does E.T. the Extra-Terrestrial, because Spielberg wanted to replicate that same familiarity with his characters—audiences don’t look for an obvious savior, but rather identify with the real people swept up in an impossible situation. Like Jaws, those films also kept a foot in reality by keeping their environments small. Viewers can reckon with the crisis in Amity and the foolish decisions made by the people in charge (its mayor refuses to close the beaches despite the shark-attack risk), just as they can follow the specific beats of how things go wrong, one by one, at John Hammond’s unopened dinosaur park.

It’s an approach that many blockbusters have failed to heed, even if a successful tale can be told on a much grander scale—look at the wide-screen success of Mad Max: Fury Road this year, or the infinite parts of the Marvel cinematic universe. Even Spielberg himself would acknowledge that his biggest error in his Jurassic Park sequel, The Lost World, was bringing a T-Rex to wreak havoc in San Diego—the story got too big, and too messy. Meanwhile, Jaws’ heroes have a simple mission: Take down an oversized shark with a couple of guns and cans of pressurized air. When the protagonists manage to triumph over the monster, it’s a success that feels truly earned, rather than dictated by formula.

Jaws might be the prototypical blockbuster, but that was more a feat of studio genius and marketing than Spielberg’s filmmaking—in the 1970s, the only films that would be crammed into hundreds of theaters on their release day were B-movies and exploitation dramas, so as to avoid bad reviews. More reputable studio films would start slowly, screening in just a few theaters, before building up to a wider release across the country over many weeks. Jaws was not the first film to buck that strategy, but it was one of the first well-reviewed films to do it, coupled with an unprecedented advertising campaign. It was a strategy that studios would refine and repeat over the next 40 years.

In honor of its anniversary, Jaws will be back in select theaters on June 21, and even if for fans who’ve seen it enough times to be prepared for every jump and twist, it still has the ability to surprise. Jurassic World, the latest heir to Jaws’s box-office throne, will likely be playing on a screen nearby. Asked to top an already perfected formula, it bemoans its legacy, meta-textually winking at the impossible task given to sequels of beloved original works. Jaws, by contrast, is a film about three men in a boat looking for a shark, and it’s all the better for it.