Do These So-Called Shark Repellants Keep Sharks at Bay?

While it's true that the number of people being bitten by sharks has risen in the last 20 years, that probably has more to do with an increase in the number of people doing water activities in the shark's' natural habitat. The fear fostered by swimming with sharks in a shared space in the ocean has fuelled a demand for an effective repellent. There are several on the market, but do they work?

Not according to Charles Huveneers, a shark ecologist at Flinders University in Australia. "The increase in the variety and availability of these products has not been matched by peer-reviewed tests," he wrote in a recent study about testing them published last summer in the scientific journal Peer.

Huveneers and his colleagues went to the Neptune Islands Marine Park, the site of the largest gathering of white sharks in Australia, and compared five top-selling shark repellent products. Freedom + Surf and the Rpela, two electric devices intended to overwhelm sharks' electroreceptors and confuse them; the Sharkbanz bracelet and the Sharkbanz leash, which claim to do the same using magnets; and Chillax surf wax, which, when applied to surfboards, gives off a smell that supposedly masks any scents that might attract sharks.

Testing the five devices separately in a number of different ways, the team recorded how close the sharks came to tuna bait, how many passes they made at it, how often they took the bait, and whether they reacted to the deterrent in an observable way. They conducted 297 trials involving 44 different sharks and observed shark interactions with the bait 1,413 times.

Freedom + Surf scored best -- it reduced the number of times a shark took the bait by more than 50 percent compared to when no repellent was used. The other products had little or no measurable efficacy on sharks going after bait. Keep in mind that Freedom + Surf, priced at $500, only fobs off sharks half the time, and a single bite can still be disastrous.

C. Huveneers, S. Whitmarsh, M. Thiele, L. Meyer, A. Fox and CJA Bradshaw, "Effectiveness of Five Personal Shark-Bite Deterrents for Surfers," PeerJ, August 31, 2018; https://doi. org/10.7717/peerj.5554

Shark-repelling jewelry is still a thing, apparently, and the latest promoters are Shea and Geoff Geist of Roeland Park, KS, who think they've found a ready market for their Shark Off bracelet. It's engineered with three different metals to create a mild electric field "that the shark's finely-tuned senses find blinding." The Shark Off website states that the bracelet got a thumbs-up by researchers during field testing at Bimini Biological Field Station Foundation, but the Geists, maybe realizing that jewelry is ineffective against sharks, write, "It's really about helping people overcome their fear, so they can enjoy the ocean."

Not that the Geists have much shark diving experience. Shea still grapples with her own fear of water, insisting that she can't even make it to the deep end of a pool. Not many sharks there, Shea.