Sharks have long captured our imagination and our fears. These ancient predators have roamed the oceans for over 450 million years, evolving into perfectly adapted hunters with remarkable sensory capabilities. While popular media often portrays sharks as mindless killing machines, the reality is far more complex and fascinating. Sharks are curious creatures with sophisticated sensing mechanisms that help them investigate their environment. Understanding what triggers a shark’s curiosity is not only scientifically interesting but also practical knowledge for ocean-goers. In this article, we’ll explore ten things that naturally pique a shark’s interest and three that surprisingly don’t, providing insight into how these magnificent creatures perceive and interact with their world.
The Science Behind Shark Curiosity
Sharks possess an impressive array of sensory systems that allow them to detect and investigate potential prey or objects of interest in their environment. Their curiosity is driven by a combination of evolutionary adaptations designed to help them survive in the dynamic ocean ecosystem. Unlike humans who primarily rely on vision, sharks employ a multi-sensory approach to investigate their surroundings.
A shark’s sensory toolkit includes electroreception through ampullae of Lorenzini (specialized organs that can detect electrical fields), an acute sense of smell capable of detecting one drop of blood in 25 gallons of water, pressure-sensitive lateral lines, excellent hearing, and vision adapted for low-light conditions. These sensory capabilities work together to create a comprehensive awareness of their environment, and when something unusual is detected, their natural curiosity is triggered to investigate further.
10. Erratic Movements and Splashing
One of the most powerful triggers for shark curiosity is erratic movement and splashing at the water’s surface. Sharks are evolutionarily programmed to investigate unusual disturbances, as these often indicate injured prey or feeding opportunities. When swimmers or surfers splash vigorously or move in unpredictable patterns, they may unintentionally mimic the movements of injured fish or marine mammals – prime targets for predatory sharks.
Research conducted by the University of Western Australia found that sharks are particularly attracted to irregular movement patterns rather than steady, predictable swimming. This is why marine safety experts often advise remaining calm if you spot a shark while swimming. Panic-induced thrashing can transform you from an uninteresting object to a potential item of curiosity for nearby sharks. Swimming steadily and deliberately away from the area is generally recommended over frantic movements.
9. Blood and Body Fluids
The exceptional olfactory capabilities of sharks make blood and body fluids powerful attractants. Contrary to popular belief, sharks can’t smell “a drop of blood from a mile away,” but their sense of smell is remarkably acute. Great white sharks can detect blood at concentrations as low as one part per million, allowing them to sense blood from up to a quarter-mile away under ideal conditions. This sensitivity evolved to help sharks locate wounded prey in vast ocean expanses.
Beyond blood, sharks are also attracted to other bodily fluids. Fish oils, urine, and sweat can all trigger a shark’s curiosity and investigative behavior. This is why spearfishers who keep caught fish attached to their bodies often face increased risk of shark encounters – the fluids released by stressed or injured fish create a sensory trail that sharks are naturally programmed to follow. For ocean-goers, this underscores the importance of not entering the water with open wounds and being aware of your surroundings when fishing activities are occurring nearby.
8. Contrast and Bright Colors
Sharks possess well-developed vision that is particularly attuned to contrast and bright colors. Research from the University of Western Australia and the Oceans Institute has demonstrated that sharks can see color, though their perception differs from humans. They are especially attracted to high-contrast objects that stand out against the ocean background. This explains why yellow, white, and silver frequently appear in studies of colors that attract shark attention – these colors create strong visual contrast in the water.
This visual attraction to contrast and bright colors has practical implications for ocean safety. Some shark experts and marine biologists recommend avoiding bright swimwear, particularly yellows and whites that create high contrast with the ocean. Instead, blues, greens, and blacks that blend with the marine environment may be less likely to trigger a shark’s visual curiosity. This principle has even informed the development of “cryptic” wetsuits designed to reduce visibility to sharks by minimizing contrast patterns that might otherwise catch their attention.
7. Electrical Signals
Perhaps the most fascinating aspect of shark sensory perception is their ability to detect electrical fields through specialized organs called the ampullae of Lorenzini. These gel-filled pores on a shark’s snout can detect extremely weak electrical currents – as low as five billionths of a volt. In nature, this remarkable ability helps sharks locate prey hidden under sand or in murky water, as all living organisms generate weak electrical fields through muscle contractions and nervous system activity.
Human activities that generate electrical fields can inadvertently trigger shark curiosity. Electronic devices like underwater cameras, dive computers, and even the electrical impulses from human heartbeats can be detected by sharks. Scientific research has demonstrated that some shark species will investigate sources of electrical stimuli, even biting electrical equipment deployed by researchers. This has led to the development of shark deterrent technologies that overwhelm these sensitive electrical receptors with strong, repulsive fields – essentially creating an electrical “fence” that sharks prefer not to cross.
6. Low-Frequency Sounds
Sharks possess an acute sense of hearing specialized for detecting low-frequency sounds that can travel long distances underwater. Studies have shown that sharks can hear sounds between 10 Hz and 800 Hz, with greatest sensitivity below 375 Hz. These low-frequency sounds are particularly interesting to sharks because they often indicate feeding activity, distressed prey, or other biologically significant events in their environment.
Activities that generate irregular, low-frequency vibrations can draw shark attention from considerable distances. The sound of a speargun, the splash of a diver entering the water, or the unusual acoustics of a swimming person can all trigger investigative behavior. Research by the University of Miami’s Shark Research Institute found that certain boat motors producing specific frequencies attracted sharks from over a mile away. This sensitivity to sound explains why areas with high levels of unusual aquatic activity – like popular diving spots or fishing areas – may experience more frequent shark encounters as the sounds generated can draw curious sharks from surrounding waters.
5. Shiny Jewelry and Reflective Objects
Shiny objects that reflect light underwater create visual stimuli that can trigger a shark’s hunting response. Jewelry, watches, metallic components on diving equipment, and even reflective zippers or buckles can create flashes of light that mimic the characteristic shimmer of fish scales. This resemblance to natural prey makes reflective items particularly interesting to sharks, who may approach to investigate these potential food sources.
Marine biologists have documented numerous cases where sharks have shown specific interest in divers’ reflective equipment or jewelry. In several documented incidents, sharks have bitten at shiny objects like camera housings or metal tank components. This behavior likely represents investigative biting rather than predatory intent, but the outcome can still be dangerous. Many ocean safety organizations recommend leaving jewelry ashore and minimizing reflective gear when entering waters where sharks are known to frequent. Some modern diving and swimming equipment is specifically designed with matte finishes to reduce potential shark interest.
4. Fish Sounds and Feeding Activity
The sounds and vibrations of fish feeding or in distress act as powerful shark attractants. When fish engage in feeding frenzies or when injured fish struggle, they produce distinctive acoustic and vibrational signatures that sharks have evolved to detect and investigate. These sounds typically indicate a potential feeding opportunity, making them irresistible to sharks who may travel considerable distances to investigate the source.
Human activities that mimic these feeding cues can unintentionally attract shark attention. Fishing practices like chumming (dispersing fish parts and blood into the water), spearfishing, or catch-and-release fishing where fish struggle on lines all create sensory cues similar to natural feeding events. Studies conducted off the coast of Australia found that the number of sharks in an area increased significantly within 30 minutes of fishing activity beginning. For ocean recreationists, this underscores the importance of maintaining distance from active fishing areas and being aware that these activities may draw sharks that might not otherwise be present.
3. Silhouettes and Shadow Patterns
When hunting, many shark species approach prey from below, where they can observe silhouettes against the lighter surface of the water. This hunting strategy makes them particularly attentive to objects creating distinctive shadows or silhouettes. Surfers on boards, for example, can create silhouettes that resemble seals or sea lions when viewed from below – preferred prey for species like great white sharks. This misidentification theory is supported by the observation that many shark bites on surfers are single “investigative” bites rather than continued feeding behavior.
The significance of silhouettes extends beyond surfboards. Swim platforms, paddleboards, and even swimming humans create shadow patterns that may trigger a shark’s curiosity. Research from the Florida Program for Shark Research suggests that sharks are more likely to approach unfamiliar silhouettes to investigate them. This visual triggering explains why many shark encounters occur in low-visibility conditions like dawn, dusk, or in murky water, when sharks rely more heavily on silhouette recognition and may make identification errors. Some newer surfboard designs now incorporate patterns on the underside specifically intended to break up the traditional surfboard silhouette and make it less seal-like when viewed from below.
2. Territorial Intrusions
While not all shark species are territorial, some display distinct territorial behaviors, particularly during breeding seasons or in areas with concentrated food resources. Bull sharks, for instance, are known to establish and defend territories in river mouths and estuaries. When humans enter these spaces, sharks may investigate the intrusion out of territorial curiosity rather than hunting interest. This defensive curiosity can manifest as close approaches, circling behavior, or exaggerated swimming postures.
Understanding shark territorial behavior is complicated by the fact that these territories are often unmarked, temporary, and invisible to human observers. Research published in the Journal of Marine Biology documented how certain shark species return to the same areas seasonally, establishing temporary territories that they defend against competitors. For ocean users, this means being particularly cautious in areas known for seasonal shark aggregations, such as breeding grounds or feeding hotspots. Local knowledge from fishermen, dive operators, and marine authorities can provide valuable information about locations where territorial behaviors might increase the likelihood of curious shark approaches.
1. Unfamiliar Odors and Chemical Signals
A shark’s sense of smell is extraordinarily sensitive to novel or unusual chemical signals in the water. While blood and natural body fluids are well-known attractants, sharks also investigate other unfamiliar odors that stand out against the background chemical composition of their environment. Sunscreen, insect repellent, perfumes, deodorants, and other artificial chemical products can create olfactory signatures that may trigger investigative behavior in sharks unaccustomed to these compounds.
Marine biologists from the Bimini Shark Lab have observed that sharks will often approach and investigate unfamiliar chemical trails, even when these aren’t associated with potential prey. This chemical curiosity likely evolved as an adaptive mechanism to help sharks identify new food sources or detect potential environmental changes. For swimmers and divers, this sensitivity suggests minimizing the use of strongly scented personal care products before entering the water in shark-inhabited areas. Some eco-friendly sunscreen manufacturers now specifically advertise their products as having minimal olfactory signatures to reduce the chance of attracting unwanted marine attention.
3. Scuba Bubbles
Contrary to what many people might expect, the bubbles produced by scuba equipment generally don’t attract sharks and may actually deter them. Research conducted by marine biologists has found that the sound and sensation of bubbles rising through the water column often causes sharks to maintain their distance rather than triggering curiosity. This bubble aversion likely stems from the fact that bubbles are not a natural phenomenon sharks associate with prey or interesting objects worthy of investigation.
This surprising finding has practical applications for divers. Some shark safety protocols recommend that if a diver encounters an overly curious shark, they should exhale a burst of bubbles toward it. The unusual sensation of bubbles flowing across a shark’s sensitive lateral line (the pressure-sensing system running along its flanks) often causes the shark to turn away. However, it’s worth noting that while bubbles themselves don’t attract sharks, the overall presence of divers—with their movements, equipment, and potential disruption of the environment—might still draw shark attention for other reasons discussed earlier.
2. Human Voices
While sharks have excellent hearing for low-frequency sounds, research has shown they show little to no interest in human voices and conversation. The frequency range of human speech (typically 85-255 Hz) falls within sharks’ hearing range, but these sounds don’t resemble the acoustic signatures of prey or biologically significant events that would normally trigger their curiosity. Multiple scientific studies, including work by the Shark Research Institute, have demonstrated that sharks rarely react to recorded human voices played underwater.
This lack of interest in human vocalization makes evolutionary sense—throughout their 450-million-year history, sharks never evolved to associate human speech patterns with food or danger. For recreational divers, this means that normal conversation through regulators or even shouting underwater to get a buddy’s attention is unlikely to attract sharks from a distance. However, it’s important to note that while the speech itself doesn’t attract sharks, the physical activities associated with producing loud underwater sounds (like vigorous movement) might still trigger interest through other sensory channels.
1. Steady, Rhythmic Swimming
Perhaps most surprisingly, sharks typically show minimal interest in humans engaged in steady, rhythmic swimming. When swimmers move with consistent, smooth strokes without erratic changes in direction or speed, they rarely trigger the predatory curiosity that irregular movements provoke. Research from shark behavior experts at the University of Miami has demonstrated that sharks are neurologically wired to notice sudden changes in movement patterns rather than constant, predictable motion.
This finding forms the basis for one of the most important safety recommendations for swimmers who encounter sharks: maintain calm, deliberate movements rather than panicking. Smooth swimming doesn’t mimic injured prey, which typically move erratically as they try to escape. By maintaining steady, purposeful swimming when sharks are present, ocean-goers present themselves as neither prey-like nor particularly interesting from a shark’s perspective. This doesn’t guarantee safety in all circumstances, but understanding that calm swimming is less likely to trigger curiosity than panicked thrashing provides an important psychological tool for managing shark encounters.
Conclusion: Understanding Shark Behavior Key Takeaways
Understanding what does and doesn’t trigger a shark’s curiosity provides valuable insights into these magnificent predators’ sensory world and helps us coexist more safely with them in their ocean home. The triggers we’ve explored—from erratic movements and blood to electrical signals and unfamiliar odors—all make evolutionary sense when we consider sharks’ specialized role as ocean predators. By recognizing these patterns, we can make informed choices about our ocean activities that minimize unnecessary shark interactions. Rather than fearing sharks, this knowledge allows us to appreciate their remarkable sensory adaptations and behavior.
It’s worth emphasizing that shark attacks remain extraordinarily rare, with only about 70-100 unprovoked attacks recorded worldwide annually, and an average of just 5-10 fatalities. You’re significantly more likely to be struck by lightning than seriously injured by a shark. By understanding what triggers shark curiosity and modifying our behavior accordingly—avoiding bright contrasting colors, removing jewelry, staying away from fishing activities, and maintaining calm movements—we can further reduce these already minimal risks while respecting these essential apex predators. Ultimately, sharks aren’t mindless monsters but sophisticated animals with complex sensory systems that deserve our respect, protection, and continued scientific study.
As a little kid, I fell in love with nature, wildlife, and animals. Living in the USA, South Africa, Italy, China and Germany gave me the opportunity to discover the world's Wildlife. My favorite animals are Mountain Gorillas, Siberian Tigers, and Great White Sharks.
I'm a certified PADI Open Water Diver, went to Everest Base Camp and Trekked Gorillas in Uganda. I hold a Master of Science in Economics and Finance.
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