A few summers ago, I rented the movie Jaws as a lark, shortly after returning from a vacation on Cape Cod. I had seen it maybe once since its blockbuster summer of 1975, and I didn’t remember much beyond the basic plot. To my surprise, it was positively riveting after so many years, right from that eerie, faint, echoing ping of sonar that you hear a split second before the opening dah-dum of John Williams’ score.

It was also campy, fun, and edge-of-your-seat scary. Moviegoers of all ages apparently agree, because nearly a generation after its release, Jaws remains a cult classic—the movie that started the summer blockbuster and stands at No. 48 in the American Film Institute’s list of the 100 greatest American movies of all time. There are people who maintain entire Web sites devoted to Jaws, endlessly debating every detail of Steven Spielberg’s first big directorial hit. For the less obsessed, an annual viewing of Jaws in the safety of your living room is a fun way to get into summer, as long as you see it after you get back from your beach vacation.

It just gets better every time, although the reasons aren’t at first obvious. There are movies whose one-liners have become far more embedded in our lexicon. (“Go ahead, make my day.”) Children born 20 years after Jaws debuted might be more familiar with its closing-in-for-the-kill theme music than its dialogue, but they probably can’t name the movie it came from, while Jaws spoofs and references fell out of comic routines a couple of decades ago.

But as a horror flick—and most critics categorize it as such—Jaws has something that Alien and Night of the Living Dead don’t: A villain that exists in the real world, a creature out there in the ocean that occasionally takes a chunk out of the surfer along with the surfboard.

It doesn’t matter that scientists now believe great whites aren’t automatically man-eaters, or even man-hunters. The underwater view of a human paddling on a surfboard apparently looks like the silhouette of a seal to Mr. Shark, and kids and dogs splashing around in the waves make the same choppy motions as wounded prey—which the shark interprets as the drive-through window at McDonald’s.

No, what counted then and now is the knowledge that one minute, you can be having fun in the water, and the next minute, you can be missing a leg, just like the guy in the movie. (And that severed leg, dropping heavily to the bottom of the pretty little salt pond, looks more convincing than the movie’s shark, even though you know it’s a fake leg.) A shark might be thinking, in shark terms, “Oops! My mistake—I thought you were a seal!” after the initial bite, but that doesn’t make Jaws one iota less terrifying.

“I don’t think it’s particularly gory—it’s scary,” says Albany writer and film critic Amy Biancolli, who reviews movies for the Houston Chronicle. “It’s such good storytelling, because it taps into primal fear.”

If you’re still not sure you’re ready to see what you’ve missed, you’ve got plenty of time to change your mind. Sharks have been around since the dinosaurs, and Jaws is probably going to be available to rent longer than that. You might try seeing the movie and skipping the book, because although the late Jaws author Peter Benchley had impeccable literary genes—he was the grandson of the humorist Robert Benchley—Jaws is one of the few Hollywood blockbusters where the movie was better than the book. For a really great read about a real great white, try Close to Shore, by Michael Capuzzo, a meticulously researched account about the shark that terrorized the New Jersey shore in the summer of 1916, an incident that is sometimes attributed as the inspiration for Benchley’s novel.

But should you first-time viewers want to impress your friends with your Jaws trivia, here are a few fun facts:

Every Memorial Day weekend, Jaws fans from all over the country converge on Martha’s Vineyard, the setting of the movie’s fictional resort town of Amity, for symposiums and sight-seeing built around the movie. The Chamber of Commerce welcomes them, says executive director Nancy Gardella. A number of Martha’s Vineyard residents who were extras in Jaws still live on the island and will regale visitors with their recollections. The chamber has a replica of the model shark used in the movie, and Gardella has seen tourists take pictures of their babies posed in its gaping jaws.

Benchley spent much of the rest of his career trying to counter the image of sharks as ocean zombies seeking their next meal of human flesh, an image for which he felt at least partly responsible. He became a spokesman for the Environmental Defense Fund and other conservation groups, and devoted his later writing to nonfiction books about sharks that underscored their valuable role in the ocean’s ecology.

A great white shark got trapped in a lagoon on Cape Cod in 2004 for about two weeks, after blundering into the confined space when the water was unusually high. The shark inspired daily updates as experts figured out how to lure it back to the open ocean. It finally swam to freedom, but, unlike the shark in Jaws, it did so without eating anyone.

Have fun in the water this summer.

—Darryl McGrath