Swimmer who vanished at Lovers Point was wearing a shark deterrent. What science says about what they do — and don’t do

After a shark attack injured one of their own nearly three years ago, members of the Kelp Krawlers — who swim weekly around Lovers Point in Monterey County — began searching for something that might make the open ocean feel safer.

They turned to wearable shark deterrents, including magnetic ankle bands designed to overwhelm a shark’s electroreceptors — the sensitive “sixth sense” pores the predators use to detect the faint electrical heartbeats of nearby prey. Other products on the market rely on electrical currents, while some use scent.

Erica Fox, a seasoned triathlete and Kelp Krawlers member, was wearing one such device Dec. 21, 2025, when she was found dead. Her body was discovered along the Davenport shoreline in Santa Cruz County, about 25 miles from where she was last seen.

Fox’s death — now under investigation and suspected to have involved a shark — has sparked scrutiny among swim club members about whether the devices meaningfully reduce risk.

A Santa Cruz County Sheriff’s Office spokesperson said the agency could not confirm whether an autopsy had been performed or whether Fox had suffered a shark bite.

Witnesses reported seeing a shark breach just offshore at Lovers Point that morning, where Fox was leading a group of about a dozen swimmers. Many of them had purchased Sharkbanz-branded products after a 2022 attack injured fellow Kelp Krawlers member Steve Bruemmer, who survived but suffered serious injuries.

Sharkbanz is among the most widely recognized brands in a field of shark deterrents marketed to swimmers, surfers and divers. Other companies include Ocean Guardian, Rpela and SharkOff, each claiming its product can repel sharks using electrical, magnetic or electromagnetic fields.

Although fatal shark attacks are extremely rare, sharks — including great whites — and their prey are common along California’s coast, making the state a natural market for products promising added protection.

Sharkbanz, for example, says its bands can deter great white sharks that are merely “investigating” prey, because the predators rely on electroreception while swimming in open water. The company also acknowledges on its website that the product does little to deter ambush attacks when great whites strike at high speeds from below.

“Sharkbanz does not claim to eliminate shark bite risk or provide a specific percentage reduction,” the company told this news organization in a statement Friday. “Shark encounters are rare, unpredictable events influenced by many environmental and biological factors, making precise risk-reduction figures scientifically unrealistic for any personal deterrent.”

Despite its limitations, Sharkbanz markets its product as “proven, effective and safe,” and says it “reduces the risk” of shark encounters by emitting electromagnetic fields.

Australian-made Rpela, a device that attaches to surfboards, says its product “makes it extremely unpleasant to be around,” adding that “extensive testing has been carried out with predatory sharks with outstanding results.” SharkOff uses a low-voltage field intended to make sharks “jerk away” from the device, while Ocean Guardian claims its product causes “harmless but unbearable spasms” that prompt sharks to swim away.

Independent research has cast doubt on many of those claims.

A 2018 Flinders University study in Australia tested five personal shark-bite deterrents — Freedom+Surf by Ocean Guardian, Rpela, Sharkbanz bracelet and leash, and Chillax Wax — during nearly 300 open-ocean trials. Only one electrical device, Freedom+ Surf, reduced shark interactions by more than half. The other products showed little or no measurable effect.

Sharkbanz disputed the study’s relevance to its products, saying the testing conditions were not designed to evaluate wearable magnetic devices as they are intended to be used.

“The use of a large, highly attractive tuna bait suspended well beyond the effective range of permanent magnets represents an extreme, worst-case scenario,” the company said.

Rpela also disputed the findings, citing an independent 2021 study published in the Journal of Marine Science and Technology-Taiwan that found its redesigned “v2” model reduced the likelihood of great white shark bites by 66% and overall interactions by 38%.

More recently, Carl Meyer, a research professor at the Hawaiʻi Institute of Marine Biology, has been studying multiple wearable shark deterrents, including Sharkbanz.

One key limitation, Meyer said, is the extremely small range of the electromagnetic field the devices emit — a range sharks are unlikely to detect until they are already very close.

“A shark has to be within about 3 feet to even detect the field from a Sharkbanz bracelet,” Meyer said. “At that distance, the field strength is well within the range of natural electromagnetic signals sharks routinely encounter. There’s nothing inherently alarming about it.”

Meyer also criticized how such products are marketed, particularly the repeated use of phrases like “reduce the risk.”

“Mainstream safety products typically provide clear, quantitative risk-reduction numbers, which I have not seen for this device,” he said.

Sharkbanz said that while magnetic deterrents have limits, independent, peer-reviewed studies have shown they can alter shark behavior at close range, including “avoidance and reduced engagement with targets.”

Many of Fox’s fellow swim club members said they were aware of the research — and its limitations.

“All of us will openly admit that we hold on to certain things, knowing that it gives us a false sense of security,” said Lisa Jensen, who swam regularly with the Kelp Krawlers. “But we do it anyway.”

Jensen and fellow swimmer Sharen Carey said a club member contacted Sharkbanz after Bruemmer’s attack in 2022, when he was pulled underwater by a great white for about 12 seconds.

“They offered all of our members a discount code,” Carey said. “And so, of course, we all got them.”

Carey said she believes the anklet Fox wore was also a Sharkbanz. “It looked like mine,” she said.

Sharkbanz said it was saddened by Fox’s death but said it had been “very straightforward” with the group about the limits of its technology, pointing to an email to a group representative that said “there is no effective way to prevent this type of ambush attack.”

The company said it likened the bands to seat belts or bike helmets, which are “intended to reduce the risk of harm, but they cannot protect someone fully, all the time.”

After researching the product herself, Carey said she understood the band offered little protection against the kind of ambush attack she feared most at Lovers Point. She wore it anyway when she swam with Fox and the group that morning.

“I’ve never gone into the water consciously saying to myself, ‘I don’t need to worry about sharks, because I have this band on,’” Carey said. “So why do I wear it? That’s a really good question, isn’t it?”