Several things can repel sharks, but no single method works perfectly or against every species. The most effective option tested so far is an electrical deterrent device, which reduced shark bites by about 54% across the three species responsible for most fatal encounters: white sharks, tiger sharks, and bull sharks. Other approaches, including magnets, visual patterns, and chemical compounds, show more mixed or limited results.
Electrical Deterrents: The Strongest Evidence
Sharks have an extraordinary sense that most animals lack. Tiny pores around their snout detect faint electrical fields in the water, which helps them locate prey buried in sand or swimming nearby. Electrical deterrent devices exploit this sensitivity by generating a field strong enough to overwhelm that sense, creating an unpleasant sensation that causes the shark to turn away.
The most rigorously tested product in this category is the Ocean Guardian Freedom+ Surf, which attaches to a surfboard and trails electrodes in the water. In independent field trials run by Flinders University using white sharks as test subjects, the device reduced bait interactions from 96% (on an unprotected board) to 40%. It was the only deterrent in the study that achieved a statistically significant reduction. Sharks also kept a greater distance from the board and made more cautious passes before approaching.
A 2024 study published in Scientific Reports expanded the testing to include bull sharks and tiger sharks alongside white sharks. The surf-mounted electrical device reduced the overall probability of bites by 54% across all three species. A diving version of the product cut tiger shark bites by 69%, but had virtually no effect on white sharks, likely because its electrodes sat farther from the target. That finding highlights an important limitation: electrode placement and proximity to the body matter enormously. The technology works, but it is not a force field. Sharks that approach from the right angle or at high speed can still make contact.
Magnets: Mostly a Myth
The idea behind magnetic shark repellents is appealing. Since sharks detect electrical fields, and moving magnets generate tiny electrical currents in saltwater, a strong magnet should theoretically irritate their senses. Rare earth magnets, particularly neodymium, have been embedded in fishing gear and consumer wristbands in hopes of reducing shark encounters.
The evidence, however, is discouraging. Research published in Scientific Reports found that the effects of rare earth magnets on sharks are “generally minimal, transitory and context-specific.” Different metals within the rare earth series produced different results depending on the shark species, and the repellent effect was inconsistent. One study even trained yellow stingrays to deliberately seek out and feed over neodymium magnets, demonstrating that these metals have no inherent repellent quality for at least some species.
In the Flinders University field trials with white sharks, neither a magnetic wristband nor a magnetic surf leash had any meaningful effect on shark behavior. Sharks interacted with bait near the magnetic leash 94% of the time, compared to 96% for the unprotected control. The magnetic wristband fared no better, and neither product achieved statistical significance as a deterrent. If you’re considering a magnetic band as your primary protection, the data suggests it will not meaningfully change your risk.
Chemical Repellents: Promising but Impractical
The most dramatic shark repellent ever observed in a lab comes from dead sharks themselves. When shark tissue decomposes, it releases a complex mix of amino acids and putrefaction products that functions as a “necromone,” essentially a chemical death signal. In controlled experiments, exposing feeding sharks to this compound triggered a spectacular alarm response. Sharks stopped eating within one minute and temporarily evacuated the area, even abandoning food they were actively consuming.
The challenge is turning this into something usable. Researchers have identified the general chemical profile of the necromone using advanced spectrometry, but the specific active ingredient within that complex mixture remains unknown. Until scientists can isolate and synthesize the exact compound responsible for the alarm response, a practical consumer product is not feasible. You cannot exactly carry decomposing shark tissue with you on a dive.
The oldest chemical repellent on record is a World War II-era formula developed by the U.S. Naval Research Laboratory for downed pilots and shipwreck survivors. It combined 80% dark water-soluble dye with 20% copper acetate. The dye created a visual screen in the water while the copper acetate provided a chemical taste deterrent. It worked under calm conditions but dissolved quickly and offered minimal protection in rough water or against already-excited sharks. No modern chemical repellent has replaced it with anything significantly better.
Visual Deterrents: Limited Testing
Sharks see the world differently than humans do. Most species that pose a threat to people see in shades of gray and are thought to rely heavily on contrast and silhouette when identifying prey. This has led researchers to experiment with wetsuit designs that might make a swimmer less recognizable or less appealing.
Researchers at Macquarie University helped develop two approaches: a camouflage wetsuit in contrasting shades of blue designed to blend with open water, and a black-and-white striped pattern meant to mimic the appearance of a banded sea snake, which some shark species seem to avoid. In one test using tuna heads placed inside barrels wrapped in wetsuit material, a tiger shark immediately struck the traditional black neoprene barrel but delayed several minutes before approaching the camouflage version. That delay could be meaningful in a real encounter, giving a swimmer time to exit the water.
The problem is that rigorous field testing of visual deterrents on humans is, for obvious reasons, nearly impossible. The barrel tests offer a signal that sharks respond differently to certain patterns, but quantifying how much protection a patterned wetsuit provides in open water remains beyond current research. Traditional solid black wetsuits do appear to be the worst option, since they create a high-contrast silhouette against lighter water.
What Actually Works for Different Activities
Your best option depends on what you’re doing in the water. For surfers, an electrode-based deterrent mounted to the board currently has the strongest evidence behind it, cutting bite risk roughly in half. That is a meaningful reduction, though it is not complete protection. For divers, the same technology exists in a body-worn format, but its effectiveness varies by species and depends on how close the electrodes sit to your body.
Layering strategies likely improves your odds. Avoiding dawn and dusk sessions, staying out of murky water, not wearing high-contrast black wetsuits, and steering clear of areas with active bait fish schools all reduce your baseline risk. An electrical deterrent on top of those behavioral choices adds a further layer.
Magnetic products, despite heavy marketing, have no significant scientific support as standalone protection against white sharks, the species involved in most serious incidents. Wax-based repellents and scent deterrents similarly failed to show meaningful effects in controlled trials. The gap between marketing claims and peer-reviewed results is wide in the shark deterrent industry, so checking whether a product has been independently tested before buying is worth the effort.