“Sharks are as timid as rabbits.” So says a superintendent of the Coast Guard, dismissing the possibility that a shark could be the culprit in an unprecedented fatal attack on a swimmer at the Jersey Shore.

It’s July 1916, a time when little is known about ocean creatures, and swimming in the sea is a relatively new pastime. Americans up and down the East Coast are shocked and mystified by the swimmer’s death. Little do they know that this is only the beginning.

A prominent surgeon at the shore, Dr. Halsey, after examining the wounds of the first victim, is the only person who believes that the creature is a shark and that it will strike again. But the public as well as the authorities—and even those who witnessed the attacks—don’t believe him. Dr. Halsey finds himself fighting widespread confusion, conspiracy theories, defiance, and outright denial of the shark.

Seeking the input of commercial fishermen, Dr. Halsey learns that they have long been concerned about a creature they call the beast. The local Native Americans, the Lenape, have their own beliefs as well.

The shark attacks occur in an already fraught time. A brutal war rages in Europe, and Americans are divided about becoming involved. Meanwhile, an unprecedented outbreak of “infantile paralysis” (polio) creates widespread panic. Into this scenario, the sea monster arrives. But what is it? Theories range from a huge mackerel to a giant sea turtle, or even a German submarine.

The story of the 1916 Jersey Shore shark, believed to be a great white, changed the way Americans think of the seashore, reminding us once again that nature plays by its own rules.