Shark-repellent ideas go from creative to weird, but the bites continue

A 14-year-old boy from Missouri was standing in knee-deep water when his foot was bitten by a shark Wednesday in Daytona Beach, Florida, a few miles from where a fellow teenager was also attacked by a shark two days before.

Those were the third and fourth reported shark bites in less than a week in Volusia County, the central Florida home to 47 miles of Atlantic Ocean beaches known for their beauty and the abundant presence of sharks. None of the injuries was life-threatening, but all were frightening and required hospital care.

A month earlier, sharks attacked a woman and two teenagers on the same day at two beaches in the Florida Gulf Coast, resulting in the loss of limbs.

In a state with by far the most confirmed unprovoked shark attacks in the country − nearly five times as many as Hawaii − and in other coastal locales, plenty of attempts have been made to prevent such incidents. Even the late Julia Child, before making her name as a chef, cookbook author and TV personality, stirred up an anti-shark recipe. Some make us feel safer. None has proven reliable.

Researchers continue their quest for the Holy Grail of shark repellents, having tried and failed over the years with tactics such as tear gas, human sweat, firefly extracts, water from crocodile habitats, and even Bengal tiger feces.

The idea of repelling sharks is alluring. Fishermen want a way to keep sharks from swiping targeted fish right off their hooks. Swimmers and surfers wish sharks would keep a comfortable distance. And tourism officials want safe beaches.

The chances of a shark attack are remote – only one in 11.5 million in the U.S., according to the Florida Museum. By comparison, the odds of getting hit by lightning are less than one in a million, based on data from the Centers for Disease Control and Prevention. In a country of 330 million people like the U.S., that's approximately 29 shark bites a year − there were 36 in 2023, more than anywhere in the world − compared to 300-plus lightning strikes.

But shark attacks can be traumatic and sometimes deadly, like the one that killed noted surfer and part-time actor Tamayo Perry in Hawaii last month. So science keeps trying to find a reliable way to keep sharks at bay.

Child used her bathtub to mix a repellent during her days with the Office of Strategic Services (America's first formal intelligence agency that later became the CIA). Her shark-repellent recipe was a mixture of copper acetate, black dye and wax that reeked like a dead shark.

The military wanted Child or others to keep curious sharks from detonating mines during World War II. It was thought to have somewhat worked for several hours after each mine was treated with the stinky concoction.

Our WWII enemies included sharks

Serious scientific efforts to develop a shark repellent began during World War II, with Child among the pioneers.

"The repellent was a critical tool during WWII, and was coated on explosives that were targeting German U-boats," the CIA's website says of Child's shark-repellent recipe. "Before the introduction of the shark repellent, curious sharks would sometimes set off the explosives when they bumped into them."

Beyond Child and the OSS, other attempts involved the Woods Hole Oceanographic Institute, the University of Florida, the Scripps Institute of Oceanography and the American Museum of Natural History. Early materials tested included chlorine gas, sodium cyanide, strychnine nitrate, narcotics, chemical warfare gases and stenches.

But later research found the wartime repellents mostly ineffective.

What about shark-repelling products? Does manipulating magnetic and electric fields work?

These days, the more promising shark repellents − but still sketchy, biologists say − are electric and magnetic in nature.

A shark's ability to smell, feel or otherwise zero in on targets from afar stands unparalleled at sea. Through a series of sensory pores in their snouts − called ampullae of Lorenzini − sharks can sense extremely weak electric fields, including those that move muscles and make hearts beat in prey.

But this variety of "animal magnetism" doesn't appear that reliable either, shark scientists say.

There are hundred-dollar-plus ankle bands that send out magnetic fields to stave off sharks, but do any of these tactics work?

The short answer is "no,'' or a hard "maybe'' for most of them, says Toby Daly-Engel, associate professor at the Florida Institute of Technology and director of its Shark Conservation Lab.

While some shark deterrents have shown promise, scientists say the results are mixed at best, so the jury's still out.

Even the studies that companies put forth to promote their products often show little or no difference in avoidance between the control (no magnet) and the test (a magnet), Daly-Engel notes.

"Sharks have electrosense, and if you mess with it, they don't like it," Daly-Engel added. "This could deter some sharks in some circumstances, maybe."

She says the studies promoting the products tend to show "limited or inconclusive data from a select few species" and most date from about a decade ago. "And there have been no magical breakthroughs in shark deterrents since then, so yeah, gimmick."

Contact Waymer at jwaymer@floridatoday.com. Follow him on X (Twitter) at @JWayEnviro.