Shark Deterrent and Detection Technology Demystified: What Works, What Doesn’t and Why
“Predatory sharks have small gel filled sacs knows as ‘Ampullae of Lorenzini’ on their snouts. They use these short range sensors when feeding or searching for food at close range. The Shark POD creates a three-dimensional electrical wave form which creates a very unpleasant sensation impacting the shark’s ‘Ampullae of Lorenzini’.

“When the shark comes into proximity of the electrical wave form (around 3-4 meters in diameter) it experiences non-damaging but uncontrollable muscular spasms causing it to flee the area.”

Sharks & Surfers

Open wide!” said Roy Scheider.

Technology is meeting sport again with the advent of various technologies to repel sharks in the hopes of reducing shark encounters and shark attacks.

A relatively new class of patented shark-repelling products (arriving on the scene in 2014, but whose R&D dates back to 2005) is garnering attention as humane and environmentally friendly. The technologies encompass a wide range of acoustic (sonar), electric, magnetic and physical barrier systems.

But do shark deterrent actually work?

What evidence is there for their efficacy- on shark encounters vs. actual shark attacks? How affordable and accessible is the technology? And do the gadgets have the negative consequence of disrupting shoreline ecosystems and harming sharks?

Our research was exhaustive, took us around the globe, and we’re proud to share it with you here!

Shark Stopper

One company, SharkStopper offers “Peace of Mind” in “Open Waters” and is actively seeking investors via Kickstarter, in order to launch two products: (1) a Personal Shark Repellent (PSR) and (2) a commercial-use Watercraft Shark Repellant.

The first is marketed to “minimize potential shark attacks against swimmers, surfers, snorkelers and just about anyone enjoying open water activities.”

SharkStopper’s PSR shark deterrent is meant to be used in shoreline waters up to 12 feet-deep.

The company says its patented technology “[…] has a dual positive effect of increasing the efficiency of the fishing industry and preserving sharks [sic] lives […] utilized as an acoustic barrier around specific coastal areas where sharks are known to encroach in swimming areas […] and will also help protect sharks from getting tangled in nets and improve the image of sharks in general.”

resp1Speaking of ‘shark PR,’ the shark advocacy group, Shark Allies, says poachers kill 100 million sharks yearly- for their fins or for sport.

There is also the practice of “culling,” defined as the selection and/or segregation of an animal for slaughter, often for the purpose of reinforcing or removing characteristics of the group.

SharkStopper’s founder, Brian Wynne, has allegedly tested the battery-charged, cell phone-light device in conjunction with shark experts- in the Bahamas, Mexican and Hawaiian waters, and in the Seattle aquarium.

Wynne tested various frequencies on various species of sharks before settling on a design that he claims is effective in deterring Bull, Tiger, Galapagos, Caribbean Reef, Lemon, Sand, Nurse, Thresher, Black Tip, Hammerhead and Great White species.

(Note: SharkStopper did not respond to our request for comment on if, or how, the effectiveness of their PSR differs among species.)

SharkStopper’s rechargeable, battery-powered device is worn around a watergoer’s ankle, like a prisoner’s ankle bracelet and emits an acoustic signal whenever it is submerged in water. According to reports, SharkStopper plans to sell its PSR for around $300.

Another company, Shark Shield (of Joondalup, Australia, and with an office in St. Petersburg, Florida), offers similar shark deterrent technology in three patented products:

(the units range in price from $599-$699 and are meant for use in varying depths of water)-  surfing/SUP, scuba diving/spearfishing and scientific/military/technical uses, respectively.

(Note: SharkStopper, also, did not respond to our request for comment on if the difference in the units lies in their signal strength.)

SharkShield technology is sold by 25 authorized retailers in the continental U.S., along with mounts, carrying cases, or a 3-Year Extended Warranty for $129.

Shark Shield makes the claim, “With Shark Shield, it’s safe to be wild,” with its units that are capable of, “Managing human and shark interactions with proven Shark Shield [sic] tech supports the conservation of sharks by removing the need for culling.” It describes the mechanism of action this way:

“Predatory sharks have small gel filled sacs knows as ‘Ampullae of Lorenzini’ on their snouts. They use these short range sensors when feeding or searching for food at close range. The Shark POD creates a three-dimensional electrical wave form which creates a very unpleasant sensation impacting the shark’s ‘Ampullae of Lorenzini’.

“When the shark comes into proximity of the electrical wave form (around 3-4 meters in diameter) it experiences non-damaging but uncontrollable muscular spasms causing it to flee the area.”1

Think of the “zing” felt when you lick the contacts of a 9-volt battery: There’s no physiologic damage, but the sensation is not pleasant.

Shark Shield says its testing dates back to 2002. The company has tested shark deterrent in South African waters and cites testimonials and research papers addressing the effectiveness of “electroreception” in sharks. One of these studies claims Shark Shield works in a very particular frequency, and at a shark’s “extremely sensitive” but short “30-60cm range.”1

In other words, the electric impulses emitted by the device don’t attract- only repel- and at close intervals. At least in theory.

We found other companies, like SURFSAFE, SHARKBANZ (which employs patented magnetic technology), and Glycon Technologies (which employs a patented shark-repellent wet suit).

Just what any avid waterman or waterwoman wanted for Christmas! Dude!

One can argue that such low-strength signals differ dramatically from the very harmful sonar that has been shown to significantly- and morbidly- affect large marine mammals like whales and seals.

The U.S. government was sued in Hawaii Federal Court in 2013 (Conservation Council for Hawaii et al. v. U.S. Dept. of Commerce and the NMFS, 2013) for approving the Navy’s testing of its low-, mid- and high-frequency sonar, along with some explosives, in the Hawaii-Southern California Training and Testing Study Area (HSTT). The plaintiffs claimed the five-year project could have deleterious effects on “at least eight protected species of marine mammals” in that acoustic environment:

“Scientists have documented mass strandings; mortal injuries, including lesions and hemorrhaging in vital organs; and behavior changes in numerous marine mammal species following naval sonar training exercises around the world,” the complaint stated.

“Underwater explosive detonations send shock waves and sound energy through the water that can kill or injure marine mammals.”2

But can acoustic or magnetic shark deterrent technology also disrupt the natural habits of sharks?

Various research teams and product developers have tested, and are still testing, the use of sonar to detect sharks in waters, but may not be considering the impact on sharks’ very sensitive hearing.

When investigating mass strandings of whales, likely the result of the use of navy sonar in open waters,

“Necropsies of the animals found gas bubbles in their tissues. This is indicative of decompression sickness, what divers call the bends, and [which] typically results from surfacing too rapidly from depth. It is believed that the whales may have dived and surfaced rapidly to escape the discomfort of the sonar on their sensitive hearing.

“ […] The nearly 100% incidence of [meningitis from Carnobacterium maltaromaticum in 18 juvenile salmon sharks stranded along the northern California and Oregon coasts between 2002 and 2007)] could have also caused ‘disorientation and confusion, which might lead the sharks to strand inadvertently.”3

Dr. A. J. Godknect, President of the Shark Foundation and Shark Info editorial staff wrote:

“Studies on LFAS (low frequency active sonar) [have] only included its effects on whales, ignoring sharks or other ocean inhabitants. Yet scientific investigation on the effects of high sound levels on bony fish and sharks allow the conclusion that LFAS also seriously disturbs or even injures these animals. The subjection of various fish to sound levels of 14- to 150 dB over several hours have led to a loss of their hearing over many weeks.”4

Godnknect says it only takes a sound 40 db higher than background noise to scare off silky sharks, lemon sharks and oceanic white-tip sharks.

Dr. Arthur Myberg of the University of Miami, an expert on fish and shark acoustic studies, told Godknect in 2012, “Noise intensities 30 to 100 times higher than those which only scare off animals will most likely cause injuries.” Myberg says the critical value for sharks is around 180 dB, which is enough to damage their sensitive inner ear.4

Godknect emphasizes that sharks have “excellent” hearing and can detect low frequency oscillations of injured fish at 100 Hz. LFA systems (low frequency arrays, which have active transmitters and passive receivers) transmit sound waves in the 100 to 500 Hz range.

According to the Navy, such waves have an actual output of 215 dB (235 dB in theory) and lie exactly in the range where, 1) sound distributes the farthest distance, 2) sharks hear the best, and 3) the greatest damage to sharks’ inner ear organs is caused.4

The sonar-emitting product Clever Buoy is getting the most attention, currently, and claims to be 100% passive when, in reality, must use both an active transmitter and passive receiver to locate sharks.

surtassWe found the Clever Buoy concept to be very similar to the Marines’ and NATO’s SURTASS (Surveillance Towed Array Sensor System), which worked at an output of more than 215 dB (140 dB is the equivalent of a gunshot and can be heard up to 380 km away underwater!) At more than 100 dB, the equivalent of a chain saw, earplugs are recommended. 4

As with the SURTASS, Clever Buoy uses a seafloor-anchored, sonar-emitting box attached to a buoy that contains the processor (receiver). The idea is that one or more of these could dot a shoreline and send a satellite signal or image to a lifeguard. Unfortunately, much more testing is required.

Yet another, Gemini Imaging Sonar, system was tested in Australia in the 1) Ocean Park Aquarium and in waters 2) off the Gold Coast, Queensland and 3) Eastern Gulf of Shark Bay.

“The Gemini 720i 300M (Tritech, UK) system operates at 720 kHz, with 120-degree horizontal and 20-degree vertical beamwidths, and an elevation of –[minus]10 degrees.” It was only tested in waters 7m- and 15m- deep, due to “logistical and time constraints.” The system recognized live and deceased sharks, but it “does not record the raw signal, but as [sic] a series of individual images, which can be reviewed as moving images,” making the instant removal of “backscatter” impossible and impractical. Backscatter also increases with the depth of detection, limiting target detection to mid-water range.5

It appears that Clever Buoy is not associated with the Gemini team (their website claiming that Clever Buoy was the brainchild of Shark Attack Mitigation Systems).

Contrary to regurgitated reports, Clever Buoy has not obtained a patent (not all that difficult to do), but the team has allegedly gotten commitments from Google and Optus (of Australia) to fund, power and translate the sonar images with the latter’s software and solar power source, respectively. (Clever Buoy ambitiously aims to make the current battery-powered system, not only solar-powered but, wave-powered.)

MarketingMag of Australia reports that “Clever Buoy was created to improve the perception of the Optus network”- “Australia’s second largest telco.” “The client brief was to change the conversation from the perceived size of the Optus network to what it can do to improve people’s lives.”

Turns out, there’s plenty of business and politics in sharks and shark deterrent technology! But let’s get back to the all-important science for a minute.

Hauwa T. Abdulkarim, a Nigerian electronics researcher, reminds us that, “The sources of noise underwater include ambient noise in the sea due to sea-state; [sic] shipping noise and wind blowing on the surface is also a significant cause of noise.” (Mitson, R.B. and Knudsen H.P., Causes and effects of underwater noise on fish abundance estimation. Aquatic Living Resources, 2003).

Abdulkarim says of these sonar systems, “The reflected signal is usually buried in noise thereby making the signal unclear with no visible pattern.” However, Abdulkarim was able to design a “matched filter,” in order to “make the given noisy signal have a visible pattern” of pulses to determine the number and distance of sharks.6

The Gemini sonar system was not tested with “movement filters,” due to the fact that their sonar head was not stationary. Testers admitted in their report, ‘[…] the resulting images [obtained by use of movement filters] often lose resolution in the moving target and the process is non-trivial if either the system is moving (even minor movements relating to wave patterns or surge) or there is significant noise e.g. cavitation from waves, vessels or animal movement.”5

So, in essence, despite the rapid efforts to deploy such sonar systems, the results are far from consistent, fully tested, and the levels of sonar emitted cannot be deemed harmless to sharks.

The Gemini team noted fairly that some of their “targets,” “[…] presumably dived to the seafloor and into the ‘blind zone,’ beneath the acoustic beam, at ranges less than 19m.5 The fact that the images returned are so “noisy” and so affected by the target’s range, position, depth and strength certainly suggest more research is needed. The positive is that lower, safer frequencies at shallow depths may still show promise for shoreline swimmers, but the prospect that anyone would rush such technology to market, and possibly change signal strengths emitted- on a whim and without governance- brings up real ethical issues.

Clever Buoy only detects “large” sharks- 6.6 feet or more in length, and within a range of 197 feet (“Shallower water may reduce the range.”) – has been tested in the Sydney Aquarium, the Abrolhos Islands (Western Australia), and is still in the R&D phase.

No one can deny there’s been an increase in the reporting of shoreline shark encounters and shark attacks in the U.S. and worldwide. But some shark experts emphasize it are humans, who are encroaching on shark territory, not the other way around.

We wanted to know if that was true.

home-photo-01We spoke with shark steward, Stefanie Brendl. Stefanie is President and Executive Director of Shark Allies, used to work with Hawaii Shark Encounters tours, and has spent many years around sharks in the water. Although she’s had some experience with various shark deterrents, she says there’s so much more that we should consider, when it comes to sharks.

“My personal experience has been with [shark] deterrents that used either electricity or magnets in some shape or form. And the result was that they worked at times, during certain conditions, on certain species.

“For example, both methods seemed to keep sharks further away on a very mellow day, when there was little stimulation in the water. But when there was a lot of current, splashing and noise or food- and when there were lots of sharks competing with each other- they [sharks] were braver and more excited, and that seemed to override any small electric pulse or magnetic energy they may have been feeling. When there was one, slow moving, mellow-but-careful shark, any small current or movement would discourage them from taking bait. I have seen tiger sharks back away from a free mealwhen a diver with a big camera housing moved too close. I believe it all depends on how interested they are.

“I have no personal experience with chemical and dye deterrents, but the military has used them for years as part of their survival suits and life boats and they seem to work, until they disperse in the water.

“That’s really the problem with anything but sound – electricity, at a small dose won’t reach very far and neither does the magnetic metal. In my opinion, it [electricity or magnetism] will have effect once the shark is up close and still moving slowly but not at a distance, or when the shark is moving too fast to even notice.

“I have no experience with sound deterrents but know sharks react very quickly to the right kind of sound that can attract them, and there are other sounds that will spook them. I believe its depends on the species and what dangers they have to worry about, and whether they have gotten used to a sound. Sharks that never see divers are spooked by the noise of scuba equipment. Once they get used to it, they pay no attention to the divers. The sound of prey gets sharks going like nothing else, i.e. a struggling, vibrating fish. In the Pacific Islands, fishermen sometimes take a empty plastic bottle and crunch it underwater to mimic the sound of reef fish eating, and sharks respond to it. I have not seen them use any sound to keep sharks away.

“I am sure sharks would get scared of the sound of something that regularly hunts them, but I don’t think many sharks in the tropics have to worry much about Orcas. Bigger sharks prey on smaller sharks, and they do not make much sound. I also think the sound has to be combined with some other sign- like other animals fleeing, or a bigger shape appearing in the water to make it more effective.

“I think the only sure, 100% deterrent is dry land. Life in the ocean is complex and conditions change so quickly. There is not one tool that works in all situations.”

Two additional companies, SharkSafe and Shark Alley, have patented yet another unique product- physical barriers- which Brendl believes show a lot of promise! Unlike controversial nets that catch turtles, dolphins and sharks that “have nothing to do with shark attacks,” looser, suspended, plastic barriers act like ‘car wash’ fringe, in the open ocean.

“Fish can actually go through it,” says Brendl, “if they force their way through it. It makes the animals not want to go through it but, if they end up stuck in it, they can go through it.”

The SharkSafe barrier is designed to deter sharks using a combination of permanent magnets and an artificial “forest” of plastic pipes that look like underwater kelp sea bamboo. The R&D, spearheaded by Craig O’Connell of the University of Massachusetts Dartmouth, uses “[…] barium-ferrite permanent magnets and barriers made of long rows of PVC pipes anchored to the sea floor. The pipes have special joints that allow them to move in the currents and waves.” 7

The idea required the collaboration of marine researchers and divers and was “based on observations that seals often flee into thickets of kelp to avoid being eaten by sharks.”7

Proof positive that innovation is often rooted in simplicity.

SharkSafe was allegedly tested for a year in the Kwa Zulu-Natal (a.k.a. “shark alley” of Cape Town) , as well as in Australian waters where 460 sharks, birds and other marine life die yearly in more lethal, physical shark deterrent systems.

The results? Despite using chum lure, SharkSafe says zero of 60 sharks swam through the plastic barriers in trials, and with no “by catch” (i.e. no unintended catch).

Not so fast, say S. Africans, who know the waters there.

Shark Alley – a S. African blog perpetuated by moniker “Megalobom”- had this to say about SharkSafe:

“Sharks are capable of ignoring man-made bullshit no matter how much funding went into it.” […] “What would be better,” is, “Put a line of [these] steel poles outside of a Wal-Mart before a Black Friday sale. The humans are drawn to the area for a reason, but my barrier lies between them and their goal. […] SharkSafe has not tried a similar study where sharks are motivated to cross though a barrier that they can’t simply swim around,” but their patents were issued anyway.

Shark Alley says SharkSafe’s trials were not scientific, and that politics were at play. They say that the best, most reliable way to forecast a shark presence is this:

“1. Go to the shore and stick your finger in the water and then stick this finger in your mouth, [sic] if it tastes salty then there are sharks there.

“2. If you’re not prepared to meet one, stay on the beach.”

If our research has proven anything, it’s that innovation in shark deterrent and detection technology is rivaled only by practical and conservationist skeptics and, based on our research, rightly so!

Hawaii Institute of Marine Biology
Hawaii Institute of Marine Biology

We end this article with the opinion of Hawaii Institute of Marine Biology, Shark Research Group’s Dr. Kim Holland. Holland and his team research the behavior, physiology and ecology of sharks and other fish.

“I and my students have quite a bit of experience and have done research looking at what sharks can detect, both magnetically and electrically. The short answer is they are extremely sensitive to electric fields and magnetic fields, and they’ve got very good hearing, as well. Most of the devices tend to dissuade sharks by using electric current, and that’s been tried by a number of companies over the years.

We actually got some money by an oil company whose gear was being damaged by shark bites, and they wanted to know if there was some way of deterring sharks, so we did quite a lot of work trying to find some sort of electrical signature that would be aversive to sharks and turn them away, which is exactly what these other companies have tried to do with various products. And the short answer to your question is that there is no known device- either commercially available or scientifically being tested- that works to deter sharks when they are motivated to attack. It’s not there.

“We’ve casually tested a couple of the commercially-available products over the years and have had sharks swim right through it. The problem is- in order to deter a shark, reliably- you need to have a current that is not just aversive but ispainful. If we were listening to someone scrape their fingers on a chalkboard, that’s aversive, and it might be enough to get us to stop what we were doing; If they gave us an electric shock in a chair, that’s something that would be painful.

So, it’s a difference between being aversive and being painful, and most of the devices that have come up over the years- because you can’t have a huge amount of electricity being used (either because you need a very large power source, or because you would shock the person wearing the system)- you need to come up with something that’s aversive, not painful, and nobody has been able to find that for sharks. So, really, the short answer to all of these questions is- and probably one of the reasons these companies are not returning your inquiries- is because none of them have really shown that they work.”

Regarding the issuance of patents on the technology out there on shark deterrent technology, Holland said this:

“There’s no doubt, that under certain circumstances, occasionally you can activate one of those systems, and a particular shark you’re looking at- whether it’s in captivity, in the open ocean, or at a tourist site- every once in a while, you can see sharks change their behavior, in response to that system being activated. But the problem is it’s not on a reliable-enough basis, and it’s not happening when the shark is motivated- in either attack mode or feeding mode. That’s the difference. You cannot have a device that is strong enough to be painful to a shark, without having a small ‘power plant’ on your back to give it enough ‘juice.’ And even if you had that, when you’d activate it, you could kill the wearer.”

In response to SharkAlly Brendl’s assessment- that if a shark’s in attack mode, nothing’s going to stop it- Holland said, “I would concur with that.”

“There’s another parallel,” said Holland. “Electric fences used with dogs… I’ve had a dog that when he really reallywanted to get out of the yard, he would put his ears back and go through it! In other words, you can see, sometimes- if you did a test with the right animal, in the right mood, with the right setup- there’s no doubt that you can see some of these devices change the animal’s behavior. The problem is that it’s not reliable, and it’s especially not reliable, if the shark’s already made up it’s mind it’s going to bite someone. I’m not disputing the fact that there are occasions when these manufacturers can see changes in the shark, but I would not want to bet the farm on it.”

When asked about the promise of the physical, dangling, plastic barriers, Holland had this to say:

“To be quite candid, I think physical barriers, like the one you just described, are the only really good way of protecting, for sure. Say you wanted to take your kid to the beach, and let them play in the shore break and go swimming, 50 yards out to sea… the best way to make people secure from sharks is to put some sort of physical barrier out, and I think that’s perfectly acceptable. I don’t see any problem with that, at all. And those dangling plastic barriers, the ‘car wash’ analogy is a good one, and I can see where that would work. Most of the sharks that would make the effort to burrow underneath that are the kind that wouldn’t bite people anyway (like white-tipped and such).”

“So, the only real failsafe is to not go in the water. The second is to come up with some sort of physical structure. Because sound or electrical stimuli, or yellow-and-black stripes on your wetsuit, or any of the other cockamamie ideas- none of them have been shown to work reliably in deterring shark behavior.”

When asked if there is an ideal distance from shore, or ideal depth for placement of a physical barrier, or if there is an ethical issue with such, Holland said this:

“No. That all comes down to economics. How much material can you afford? Who’s going to maintain/service it? Is it going to be paid for by a hotel or the county? I don’t [see an ethical problem]. We’re not talking about a lot of territory; we’d only be talking- at the max- an area the size of a football field. It’s not as if you’re disturbing animals in their entire range. I can easily see a hotel on Maui getting the right permits- it being a task, given the permitting in Hawaii- but I can see why it would be attractive to hotels over there. Say 300 yards of the beach, and 50 yards offshore, and that’s almost certain to keep any ‘bad guys’ out. Of course, that won’t do anything for surfers or snorkelers far offshore, but that would probably be okay for the majority of people that just want to go for a swim and play in the shore break, and [would] work for snorkelers within the first 25 or 30 yards from shore.”

We asked Holland the most basic question of oceangoers afraid of sharks: What would you recommend for anyone who actually encounters a shark?

“The most recent shark attacks [on Oahu] are a classic example of the number one safety rule. The number one safety rule is do not go in the water by yourself! That’s because, if you do get attacked, there’s somebody out there to call for help, to help you go to shore, or to help put a tourniquet around you. Don’t go in the water by yourself and, if you are by yourself, find a place where there are other people in the water.”


1 Electroreception in vertebrates and invertebrates. S.P. Collins et al., 2010.

2 Last Ditch Effort To Save Whales From Navy. Courthouse News Service, December 2013.

3 Meningoencephalitis associated with Carnobacterium maltaromaticaum-like bacteria in stranded juvenile salmon sharks (Lamna ditropsis). PA Schaffer et al. Veterinary Pathology, April 2012.

4 Remote detection sonar threatens the oceans. Dr. Alexander J. Godknect. Shark Foundation and Shark Info, December 2002.

5 Detection of Sharks with the Gemini Imaging Sonar. Miles J. G. Parsons, et al. Centre for Marine Science and Technology, Curtin University, Perth, Australia. Acoustics Australia, Vol. 42, No. 3, December 2014.

6 Detecting the Position and Number of Sharks in the Sea using SONAR Technique. Hauwa T. Abdulkarim, Department of Electrical/Electronic Technology, School of Technical Education, Minna, Nigeria. World Congress on Engineering, July 2015.

7 Plastic kelp to keep sharks at bay. Tony Carnie. SciTech, July 15, 2014.


Article by Purna Nemani of Aloha Tech Writers (collaborator, Stefanie Brendl of Shark Allies). All rights reserved. Full and proper citation is required. Video and Photos added by Wave Tribe.

Derek Dodds

Derek Dodds is founder of the world's first ecological surf company Wave Tribe, surfboard shaper, world traveler, author and Mini Simmons enthusiast.

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Derek Dodds | Surfer, Shaper, Traveler
I'm Derek Dodds, the guy behind I love surfing, shaping, adventure travel, IPAs, useful gear, and all things related to the sea.
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