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How Shark Repellents Work

Understandably there are skeptics in world of shark repellents. Some because the mechanisms can be difficult to understand. Some because, well, we’re talking about freakin’ sharks here! With 450+ million years of evolution behind them, sharks can seem like omnipotent apex predators. But they are just trying to survive like the rest of us. And with all that evolution behind them, they are understandably better at it than most. Shark repellents use those advanced survival skills against them.

Elasmobranchs

You can really reduce the current shark repellent/deterrent technologies into three categories: visual, odorous (smell) and electrical. We’re going to briefly break those down for you (because you could literally get a PHD studying any of these). There’s a ton of foundational biology that is behind these technologies, but we’re not here to teach Elasmobranchs 101 here. For an outstanding paper on the many sensory abilities of sharks please CLICK HERE.

To understand why these innovations work, it’s important to know one vital piece of information. We are not shark food. In fact, we are actually bad for sharks’ digestive systems. We’re too crunchy (boney), too stringy and too lean. We don’t provide enough calories (fat) for the trouble and we block them up for days.

So, sharks don’t actually want to eat you. People don’t get eaten by sharks, they get bitten. Because sharks don’t have hands to reach out and touch you, and they can’t ask you what you are, they use their mouths to test things out. In the case of unprovoked shark attacks, it’s an investigatory bite. An accident really.

Shark With Diver

If you swim around looking like a shark’s favorite meal a seal (like surfers) or are literally wearing their food (like spear fishermen), then it’s an understandable case of mistaken identity. Another common mistake comes when sharks chase bait fish into murky beach waters and come across someone frolicking in the waves. These incidents fall under the classification of “unprovoked” attacks and are where repellents/deterrents will work best.

As you might expect from the world’s first true apex predator, these 450 million-year-old creatures did not swim to the top by being passive. They can be intelligent, aggressive, territorial and protective. If you provoke them, you’re gonna have a bad day no matter what you’re wearing or carrying. These attacks fall under the “provoked” classification. We’re sorry, but there’s not a lot going to help you there.

In either case, provoked or unprovoked, whether or not you live through a shark attack is of little concern to the shark.

Danger Sharks

Now let’s get back to the exciting world of shark repellents/deterrents. The first on the list, visual, is really a deterrent, not a repellent. Deterrents are more passive, and repellents are more active in nature. Visual deterrents are pretty much what you might imagine – they trick the shark’s eyes.

Surfer From Below

These visual deterrents primarily act as camouflage, much like hunting or military camouflage. Being the bad ass ambush predators they are, sharks are instinctively drawn to the silhouettes of their favorite foods. Imagine what the silhouette of a seal swimming above, would look like from the darkness below, with the sunlight as a backdrop. Surfers look much the same.

In this market these camouflages have come out as wetsuits, surfboards, and surfboard stickers. Some use actual digital images of water or blue shades of watery shapes, and others use contrasting stripes that break up the shark’s visual field.

Interestingly, there are also stickers of eyes to put on the bottom of your surfboard that seem to have some evidence of working, even if anecdotal.

Shark Repellant

Next on the list is odorous (smell). We jokingly call this technology “Eau de Dead Shark” (like some kind of fancy perfume). But the deterrent effects are no joke. In our opinion, this method is the most effective of all the deterrents/repellents.

Everyone’s heard that sharks can smell blood in the water for miles, which is true, and that’s why this works well against them. Whereas the visual deterrents use the shark’s poor visual acuity against them, this bombards their finely tuned sense of smell with the scent of rotting shark. And they hate it!

You wouldn’t think of sharks as being sentimental, or scaredy-cats, so maybe 450+ million years of survival instincts drive them away from death. In the Bahamas, where we studied the effects of Shark OFF, it was not uncommon for schools of sharks to disappear for days or weeks after one of their own was killed by a local.

As effective as the rotting shark smell is, there are a couple notable downsides. The introduction system is basically an aerosol stink bomb. Pull the pin and it fires off its contents to create a cloud of underwater stink. The cloud will begin to dissipate after about 30 minutes. You also have to know the sharks are coming, which can be problematic with an ambush hunter. The pressurized can may also not work much below 30 feet deep.

Caution Electricty

Finally, there is the pool we swim in (yeah, there’s no end to the puns in this biz) – electrical. To really understand how this works you may need to go back to that sensory biology paper we linked out earlier. You know that sharks can smell blood (or dead shark) from miles away. What a lot of people don’t know is sharks can detect minute electrical fields.

Like really, really minute – five-one billionths of a volt. Scientists believe this sense might be so fine that it would allow sharks to navigate using the Earth’s electromagnetic fields. More than that, it makes them wicked hunters. They can feel the tiny electric impulse of a fish’s heartbeat. Or panicked muscle contractions.

Shark Nose

These sensory organs are called ampullae of Lorenzini (how’s that for a mouthful). All elasmobranchs (sharks and rays) have them. The next time you see a close-up picture of a shark’s snout you will notice what looks like freckles. Those are the ampullae of Lorenzini. (You will never look a shark the same again. You’re welcome!)

As with the others, the electrical deterrents use the shark’s senses against them. Within these electrical deterrents there are three subcategories: powered, magnetic and our electro-chemical.

There are a couple of current (get it? current?) powered configurations on the market. Australia notably is working with this technology to develop electric barriers to protect recreational beach areas with high incidents of attacks. It’s an interesting endeavor that we’re following closely and hope it succeeds. The other configuration for personal use is a large battery pack powered unit for divers and surfers. This also appears to be effective although bulky, heavy and expensive.

Shark In Wave

The next category is magnetic. This technology was discovered and patented by the same scientists at SharkDefense Technologies that discovered the rotting shark deterrent. SharkDefense also discovered and patented our electrochemical repellent. It works on the same sensitive ampullae of Lorenzini. In fact, much of the research done on the magnetic repellent crosses over with ours since the method of reception is essentially the same.

Because of well-written and effectively-protected patents filed by SharkDefense there is only one player in the magnetic repellent market. And one player in the electrochemical market – Shark OFF. Although effectively utilizing the same senses against the sharks these two technologies have key differences.

The magnetic bands are larger and use powerful permanent magnets to disrupt the shark’s ampullae of Lorenzini. The housing is likewise larger and utilitarian. And they require special handling and packaging to prevent the magnets from damaging sensitive electronics. That said, if I were a surfer or diver that spent a great deal of time in the water, I would seriously consider this route.

Point Towards Shark

Shark OFF’s proprietary active element actually creates its own electric field through a process called hydrolysis. This low voltage field (think AA battery, about 1.5 volts) is imperceptible to us. To the shark’s five-one-billionths-of-a-volt sensitivity, it’s blinding. Think kryptonite for sharks. The downside of this technology is that as it hydrolyzes, it dissolves. Sort of like an Alka-Seltzer, except over hundreds of hours.

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