It was a quiet evening at sea in the waning days of World War II. The USS Indianapolis had just delivered the crucial components of the atomic bomb that would level Hiroshima to a naval base on the Mariana Islands. Their part in that grim undertaking complete, they sailed on toward the Philippines.

But another calamity lay ahead.

On the night of July 30, 1945, as the Indianapolis skimmed over calm seas in the Pacific, two Japanese torpedoes struck the ship and ripped it nearly in two. The impact and subsequent explosion immediately killed 100 crew members. More would drown as the wounded ship dropped beneath the waves. Those who survived would be faced with what has been called the worst shark attack in history, a five-day, frenzied onslaught that killed scores of sailors.

“You hear a blood-curdling scream,” Corp. Edgar Harrell recalled to the Indianapolis Star last year. “And then the body would go under, and then that life vest popped back up.”

Decades later, the Indianapolis disaster looms large in America’s collective shark consciousness. It prompted the military to pump funding into anti-shark research. It was cited in a rousing speech in the 1975 movie “Jaws.” It’s been the subject of lengthy books and a Discovery Channel “Shark Week” special.

And even though we’ve never had a comparable disaster since — the U.S. hasn’t seen a shark fatality since 2013 and more Americans are killed by spiders, cows or dogs each year than by sharks — we’re still terrified by these ocean predators. Recent news of attacks along the beaches of the Carolinas has alarmed beach goers and puzzled experts. A string of seven fatal attacks near Australia prompted the country to “cull” the sharks near its western shores last year.

Many have pointed out that, scary though those bites were, far more people are injured or killed by other animals which much less fanfare. There isn’t a story every time someone goes to the hospital with an allergic reaction to a bee sting, for example.

No, there’s something about these predators that simultaneously frightens and fascinates us. And in many ways, that captivating cocktail of thrill and terror originated in the open waters of the Pacific 70 years ago.

According to a 2001 study in the journal “Injury” titled “The Anatomy of a Shark Attack” (sounds like a nice, heartwarming read, doesn’t it?), few people spent much time considering death by shark before the 1930s. When four people were killed and a fifth injured in a Great White’s deadly spree on the Jersey Shore in 1916, people speculated that the attacker may have been a sea turtle, because sharks were so far from their minds at the time.

But attacks on Navy personnel during World War II — particularly what happened to the USS Indianapolis — turned the once-overlooked predators into the sea’s most reviled villains.

Granted, the stories from survivors of the ordeal are horrifying. Drawn up to the surface by the blood, the noise and the thrashing of the survivors, a massive group of oceanic white tips — a deadly species of deep sea-dwelling shark, usually 10 feet long from blunt snout to rudder-shaped tail — converged on the wreckage of the sunken ship, feeding first on the dead, then attacking the living.

“They stalked for hours, going around and around,” Gus Kay, who survived the attack, told author Doug Stanton for his book “In Harm’s Way.”

“We thrashed, trying to keep ’em away from us, but they came right into the group,” he continued. “… Tore guys’ limbs off. The water was bloody.”

When the men were finally rescued on their fourth day in the water, by a U.S. military plane that just happened to be flying overhead, only roughly 300 of them (out of nearly 1,200) were still alive, according to the Star.

It’s not clear how many men died from shark bites — estimates range from a few dozen to 150. In 1980, survivor Giles McCoy estimated to The Washington Post that the number of shark victims was between 60 and 80.

The saga of the Indianapolis was kept quiet by the military for years (many allege that’s because the Navy didn’t want to acknowledge its failure to find the missing men in the initial days after the disaster). But as the story slowly became public knowledge, it added to the view of sharks as vicious killers — after all, what is more disturbing than the idea of frenzied predatory fish feeding on America’s own soldiers as they drifted, injured and alone, in the fathomless sea?

The movie “Jaws,” which devotes a lengthy scene to an (embellished) recounting of the Indianapolis incident, did not help sharks’ reputation much. Nor did “Shark Week“, which debuted in 1988 with a segment called “Caged in Fear.”

Terror of sharks hits on nearly every one of the anxieties that psychologists say feed into irrational fears. They are unfamiliar — residents of a watery world we don’t fully understand — and are “mythologized” as scary. They make us feel physically vulnerable, with their hulking mass and gnashing teeth, and they remind of us of our own inability to protect ourselves. After all, the most recent bite victim in North Carolina was attacked directly in front of the lifeguard stand.

But “Shark Week’s” success — the annual extravaganza draws more than 30 million viewers each year — points to another facet of our fixation.

Much as we revile sharks, we’re also riveted by them.

“It’s kind of like a campfire tale,” “Shark Week” executive producer Brooke Runnette told the Atlantic in 2012, referring to the grisly first-hand accounts and wide-eyed cautionary tales that characterize much of the program.

She may be onto something. On a basic, biological level, humans enjoy being scared, especially when, as is true with sharks, the actual threat to ourselves is fairly minimal. Margee Kerr, a “scare specialist” who teaches sociology and works on the staff of a haunted house in Pittsburgh, told the Atlantic that thrill-seeking — horror movies, haunted houses, ghost stories, jumping off cliffs — gives the brain an intoxicating rush of chemicals associated with danger (adrenaline, dopamine, etc.) without the possibility of harm. And our brains, which are evolved to process actual threat at lightning speed, are able to enjoy the endorphins without all the fear.

“Humans have been scaring themselves and each other since the birth of the species, through all kinds of methods like storytelling, jumping off cliffs, and popping out to startle each other from the recesses of some dark cave,” she said. “And we’ve done this for lots of different reasons—to build group unity, to prepare kids for life in the scary world, and, of course, to control behavior.”

Sociologists believe that seeking out the things that scare us most may be a survival tactic. We tune into “Shark Week,” recite in hushed tones the saga of the USS Indianapolis and are riveted by the grisly attacks in the mid-Atlantic because we have an innate need to know about shark attacks. We love to know about them.

“We are not afraid of predators, we’re transfixed by them,” sociobiologist E.O. Wilson famously wrote, “prone to weave stories and fables and chatter endlessly about them, because fascination creates preparedness, and preparedness, survival. In a deeply tribal way, we love our monsters.”