Are shark repellents effective at protecting swimmers in the ocean?

By Ashley Williams, AccuWeather staff writer

The sight of a shark circling beneath a swimmer’s feet as they enjoy a dip in the ocean is enough to send any unsuspecting beachgoer into a state of panic.

However, the odds of getting attacked and killed by a shark are one in 3,748,067, according to the International Wildlife Museum.

“There are more deaths every year from vending machines and coconuts,” said Apryl Boyle, founder and CEO of El Porto Shark, an organization that analyzes and forecasts shark population data.

“There are an average of 10 shark attacks every year globally,” Boyle added. “Sharks have killed approximately 50 people in the last century, while humans kill 11,000 sharks every hour.”

Despite the low risk, there are shark-deterrent devices that aim to keep sharks away from swimmers.

The big question is: are these devices actually effective?

Diver and sharks - Getty Images

(Photo/solarseven/Getty Images)

“[Swimmers] cannot rely on any of these devices to protect them when they’re in the water,” Newport Aquarium’s Senior Research Scientist, Dr. Nick Whitney, told AccuWeather.

“Several have been tested and shown some success with certain sharks, but I’m not aware of any that have shown to be consistently effective with multiple species in multiple situations,” Whitney said.

Types of repellents include sprays like the one developed by SharkTec, which comes in an aerosol can containing an extract of dead shark tissue. The product’s effectiveness is based on evidence that living sharks aren’t fond of a dead shark's scent.

“When a shark smells decaying shark tissue, its natural fight-or-flight response kicks in and the shark will avoid that area for fear of further danger,” it states on the company’s website.

Researchers in the early 1990s originally proposed the theory of repelling living sharks by using semiochemicals as shark repellents, according to the company.

Sprays might only be effective if a swimmer, snorkeler or scuba diver has time to activate them before an impending shark attack, according to product reviewers with Ocean Guardian.

There is also a wearable acoustic repellent that aims to keep sharks away via a small plastic band that emits a blend of orca calls and a special frequency, according to SharkStopper, as killer whales tend to eat sharks.

The company states that testing has proved successful in repelling more than 15 different types of sharks, including the great white, tiger, bull and hammerhead species.

Electrical shark repellents emit a small electrical current into the water that interferes with a shark’s special sensing organs, which detect tiny electrical currents given off by a shark’s prey, according to Ocean Guardian.

When these sensory organs, called ampullae of Lorenzini, are overstimulated, they spasm and force the shark to turn away. Brands like SurfSafe and NoShark manufacture electrical deterrents.

Some products, like Sharkbanz, use magnetic technology to ‘stun’ the shark painlessly, which triggers a sensation similar to having a bright light shined in one’s eyes.

“Sharks have the most sensitive and powerful electrical sense of any animals in the world,” Nathan Garrison, Sharkbanz co-founder and director of marketing and sales, told AccuWeather.

“When a shark comes near the field that’s put out by Sharkbanz, it tells them that it might be potentially harmful and that they should turn away,” Garrison said.

The bands, which come in neutral colors that blend with clothing or water tones, fared well during testing in the Bahamas on bull sharks, the most aggressive shark species.

“The device was placed on a dummy in the middle of a feeding frenzy, and not once was that dummy attacked,” the company reported. “Without the device, the dummy was attacked once every 42 seconds.”

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In 2016, a South Florida surfer was attacked while wearing a Sharkbanz product, but the company said in that situation, no shark-deterrent device would’ve prevented it.

“At the end of the ride, he jumped off his board as the wave closed out and was bitten within a moment of hitting the water,” Garrison said. “It was just a case of terrible luck where he startled the shark, and it reacted defensively.”

Garrison added that Sharkbanz is designed to protect people from investigative and curious sharks that might mistake humans for prey.

Experts agree that whether equipped with shark-deterrent devices or not, swimmers should be aware of their surroundings.

“If you go to the beach and you’re seeing large schools of bait fish and birds feeding on those fish, there’s a good chance that there are larger fish also feeding on them, including sharks,” Whitney said.

It would be great if there were some fool-proof method that people could use, but there are so many different species that feed so many different ways that it would be difficult to have one solution that you could just wear or have with you that would keep you safe from a shark bite,” he added.

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