Do Shark Repellents Work? (Pros, Cons & Recommendation)

Whether you’re swimming, diving, or surfing, ocean recreation puts you in a place that could make you vulnerable.

Specifically, this means shark habitat.

Concerns regarding shark encounters or even shark attacks are always top-of-mind, simply because sharks are some of the world’s best predators.

However, sharks don’t actually see humans as food — in fact, we don’t even taste good to them.

Many shark bites are cases of mistaking a human for another marine animal that is their prey. And while it’s nice to know they don’t often intentionally come after people, it’s not the most reassuring thing that they can and do still bite.

Though bites and attacks are extremely rare, scientists have been researching ways to reduce shark encounters for almost a century.

So let’s take a look at the big question: Do shark repellents work? Are they necessary for avid surfers and divers?

Don’t worry, it’s not real! – Photo by lforce/Flickr

Research is mixed on whether shark repellents work. At best, some have shown to be effective about 60% of the time, but only when a shark is already extremely close by. However, there’s great debate on whether the testing and data is even reliable at this point.

Shark repellents certainly won’t increase your likelihood of a shark encounter, so there’s no harm in trying one. However, shark attacks are extraordinarily rare all over the globe, so for most people, it’s not worth investing in a shark repellent.

Let’s learn more about the different types of shark repellents and how (and whether) they work!

What is a shark repellent?

“Shark repellent” is a broad term used to refer to any device or technology meant to discourage the approach of sharks within an area.

It’s the same type of term used to describe other animal repellents, though the technology is quite different than, say, most insect repellents.

There are a few naturally occurring shark repellents, and there is ongoing research into the efficacy and development of these.

Generally, naturally occurring repellents are found in secretions or chemicals produced by animals that share habitat with sharks.

Other natural methods are derived from dead animal matter, which has a tendency to repel most animals, in water or on land.

Modern shark repellents — and the technologies we see today that came from these early versions — first began around the 1940s and saw their first major uses during World War II, when research into the topic began to take off.

In these early days, the motive for a shark repellent was largely related to the military, with the goal of decreasing the risk of stranded sailors encountering sharks.

Research has continued since then.

Considering how rare shark attacks are, it is difficult to record significant results, and there is disagreement as to whether shark repellents are effective enough to be used widely, or even if some types work at all.

Different types of shark repellents explained

There are several different types of shark repellent, based on different technologies:

  • magnetic shark repellents
  • electrical shark repellents
  • electropositive shark repellents
  • and semiochemicals.

There is some contradiction within the scientific community, as research done on each of these types can produce varying results, even in relatively controlled environments.

The different technologies show up in different ways across manufacturers and products.

Some can be worn on the wrist or ankle, some can be sprayed on, some are attachments for surfing gear like leashes, and some are even infused into wetsuits.

The technologies, though, are based in the same fundamentals, and the theories behind how they work are valid.

Magnetic shark repellent

Magnetic shark repellents use, unsurprisingly, a set of permanent magnets that overwhelm the electro-senses of sharks and similar marine animals.

It’s one of the newer methods, initially developed in 2004. Sharks are a family of animals that are sensitive to magnetic and electric fields, particularly in close proximity.

As they swim through such fields, it disrupts their senses and discourages the shark from continuing into the field.

Electrical shark repellent

Electric devices like the notable Freedom + Surf device are based in technology that repels sharks by overwhelming the electroceptors in their brains, the same biological system targeted by the magnetic technology.

These devices emit electrical pulses aimed at a shark’s electro-sensory system.

These are the most common type of shark repellent device available, though each different product is manufactured in a slightly different way, with varying efficacy.

Electropositive shark repellent

Electropositive devices are the newest type of shark repellent technology, and they function by producing a voltage.

Similar to the previous two methods, this effect of this type of voltage is specific to sharks and similar marine animals due to their biology — the voltage overwhelms their sensory systems and discourages them from staying within its reach.

Interestingly, the voltage is produced through a chemical reaction simply by immersing the metal of the device in seawater, which is a chemical electrolyte.

Semiochemical shark repellent

Semiochemical devices are fundamentally different from the other three methods discussed.

Rather than producing any sort of electric or magnetic field, this method turns to biology to send chemical signals to the shark that induce its natural responses.

These chemicals can include allomones, pheromones, and kairomones, and they trigger a “flight” reaction when found naturally.

Research is ongoing to develop the optimal formula to be used as a commercial shark repellent.

Other naturally-derived shark repellents

Other methods for producing a shark repellent formula are based in creating an extract or formula of dead animal matter, specifically shark flesh itself.

Research findings are mixed around this method, with large variances depending on which species of shark is present.

Scientists are still looking into creating a universally effective substance from either dead sharks or, notably, synthesized chemicals that replicate the same effects.

Are shark repellents necessary or worth it?

All in all, the different technologies for shark repellents can have varying results, and none of them are 100% effective.

Over the last several decades, teams of scientists across the world have dived into the details on shark repellents, and how effective they actually are.

In theory, these repellents use methods like electrical currents, magnetic fields, and olfactory stimulants to deter sharks from approaching the device (and the wearer).

It’s a difficult concept to test, since the results depend on baiting various species of sharks and recording whether or not they take the bait when a repellent is or isn’t present.

Even the most effective shark repellents are only shown to work in 60% of situations, and a dangerous situation with a shark in natural environments is already exceedingly unlikely.

In some examples of thorough testing, while the repellents were moderately successful in discouraging the sharks’ approach, they were only effective at a very short distance — less than 3 meters.

This means that the repellent is only capable of preventing a shark that is already quite close to you from coming even closer, but it can’t entirely prevent a shark from getting into your personal bubble.

Plus, shark repellents have different results from species to species — a method that could be reliable against bull sharks might have no effect against other common species.

Among communities of regular ocean-goers, the consensus is generally that shark repellents are not worth the money — even for scuba divers, surfers, and people who spend a lot of time in the open water.

Rather, there are other methods to keep yourself safer while out on the water, including getting educated on shark behavior and local habitat, and learning from experts how you should behave as a swimmer or surfer to stay cautious and respectful of these ocean predators.

How likely is a shark attack without shark repellent?

While shark repellent can help give peace of mind to the average vacationer, greater peace of mind can come from simply taking things into perspective.

This is to say, shark attacks are extremely rare. The odds of getting attacked by a shark are 1 in more than 3 million.

No matter how you look at it, the chances of being attacked by a shark are so low that we almost can’t comprehend it with numbers!

You are much, much more likely to suffer from an injury simply going about your daily life.

You’re even more likely to experience a different dangerous event than you are to be attacked by a shark — for example, you’re more likely to be struck by lightning.

Wrapping Up & Final Verdict

The science behind shark repellents is valid, but in practice, using a shark repellent can largely come down to personal preference.

If it helps you feel more secure to have a little extra protection, then shark repellents can be exactly what you need.

However, even without a shark repellent, your chances of having a dangerous shark encounter are extremely low — follow all guidelines and advisories from officials, and your ocean recreation will likely be just fine.

For more safety guides, see:

Hope this helps!