Do Shark Deterrents Actually Even Work?

Some people seek out ways to spend time with sharks and plan vacations to places like Coco Island, Costa Rica, which is known for having one of the world's best shark dives. Then, there are others who avoid the ocean altogether for fear of encountering the marine predator. Even if you're mindful of the things that attract sharks while you're swimming and snorkeling, you might still be hoping for a way to ensure that sharks don't get too close. Making eye contact with a shark can be one way to help keep it away, but there are also a variety of shark repellents on the market. 

Islands spoke with Kristyn Plancarte, marine biologist and educational content creator, to get her thoughts on these devices and whether or not they have any real impact on keeping sharks away from you. There are three basic types of shark deterrents: electrical, magnetic, and chemical. Of the three, an electrical deterrent is your best bet. Plancarte tells us, "An independent study showed that some electrical deterrent devices can be effective in repelling sharks."

Sharks are particularly sensitive to electricity, and the device temporarily impacts a shark's ability to sense electric currents. This deterrent won't have any long-term impacts on the shark, as the effect wears off as the shark moves away from the device. Plancarte explains, "Some scientists have compared the effect on sharks to accidentally looking into a light momentarily for humans."

A scientific study from 2018 placed a variety of shark-repellent devices on the bottom of a surfboard and found that the Shark Shield by Freedom + Surf was the most successful in deterring sharks (via PubMed Central). Other devices that were tested, including a magnetic band, magnetic leash, and a different electric repellent device, had little to no impact on shark behavior. It's important to note that no device will keep sharks away from you 100% of the time. Plancarte says, "The brand Freedom + Surf effectively deterred sharks roughly 60% of the time." However, it is very unlikely that you will get attacked by a shark.

Surfers are perhaps most susceptible to shark attacks because the animals may confuse a surfer (which it doesn't want to eat) with a seal (which it does want to snack on). The silhouette of a seal and a surfboard can look quite similar from below. So if you're someone who likes to surf, particularly at some of the world's most shark-infested beaches, an electrical deterrent could add another layer of protection and help you feel more at ease in the water.