The Surprising Truth About Colours and Shark Behaviour
When we think about swimming in the ocean, a primal question often surfaces: what colour are sharks scared of? It’s a query born from a desire to be safer in their world, to hold some secret knowledge that might offer protection. The simple answer, however, is perhaps not what you’d expect. There isn’t a single magic colour that will reliably frighten away a shark. Instead, the fascinating truth lies in a much more complex and intriguing interplay of biology, contrast, and pattern recognition.
For decades, myths have swirled around this topic, with “Yum Yum Yellow” being the most famous, suggesting that bright yellow is a dinner bell for sharks. But as marine science has advanced, our understanding of how sharks perceive their environment has deepened significantly. It seems the key isn’t about scaring them with a specific hue, but rather about not attracting their curiosity in the first place, or even presenting a visual signal they’ve learned to avoid.
This article will take a deep dive into the science of shark vision, deconstruct popular myths, and explore the patterns and shades that research suggests are most effective for shark safety. We’ll explore whether sharks are truly colorblind, why high-contrast shades might be problematic, and how innovative wetsuit designs are leveraging nature’s own warning signals to deter these magnificent apex predators.
Understanding Shark Vision: Can Sharks Even See Colour?
Before we can determine what colour might scare a shark, we have to ask a more fundamental question: can sharks even see in colour? For humans, colour is a rich and vibrant part of our visual experience. Our eyes contain two types of photoreceptor cells: rods (for low-light, black-and-white vision) and cones (for bright light and colour vision). It’s the variety of cones in our retinas that allows us to perceive a full spectrum of hues.
For a long time, it was assumed that sharks, as masters of their aquatic domain, must have similarly sophisticated vision. However, extensive research into the anatomy of the shark eye tells a different story. Studies conducted by researchers, including a key paper from the University of Western Australia, examined the retinas of 17 different shark species. The findings were revealing:
- Dominated by Rods: Shark eyes are packed with rod cells. This gives them exceptional vision in dim, murky, or deep water, allowing them to detect movement and shapes with incredible sensitivity, especially during dawn and dusk, which are their primary hunting times.
- A Lack of Cones: In the vast majority of shark species studied, scientists found only one type of cone cell, or in some cases, no cones at all. To perceive colour, an animal needs at least two different types of cone cells to compare the wavelengths of light. With only one type, an animal is essentially colourblind, perceiving the world in varying shades of a single colour—effectively, in monochrome.
So, what does this mean? It strongly suggests that most sharks are, for all intents and purposes, colourblind. They don’t see a yellow wetsuit as “yellow” or a blue ocean as “blue.” Instead, they perceive the world in a brilliant grayscale, like a black-and-white photograph. Their visual system is exquisitely tuned to detect contrast, shadow, and silhouette against the backdrop of the water.
This biological fact completely changes our approach to the question. The focus must shift from “what colour do sharks hate?” to “what level of contrast provokes or deters a shark?”
The Great Colour Debate: It’s All About Contrast, Not Hue
If sharks see in shades of grey, then any bright, solid colour will simply register as a light grey object against a darker grey background (the water). This is where the concept of contrast becomes critically important. A shark’s hunting instinct is triggered by objects that stand out from their environment.
Consider the natural camouflage of a shark’s typical prey. Many fish exhibit a trait called countershading—they have dark backs and light bellies. When viewed from above, their dark back blends in with the deep, dark water below. When viewed from below, their light belly blends in with the bright, sunlit surface. This makes them incredibly difficult to spot.
Now, imagine a person in the water. A surfer in a bright yellow, orange, or even white rash guard creates a stark, high-contrast silhouette. From a shark’s perspective, this solid, bright object doesn’t blend in at all. It screams, “I am something different!” This high contrast can pique a shark’s natural curiosity. Sharks are inherently inquisitive, and one of the primary ways they investigate an unknown object is with a “test bite.” This is often mistaken for a predatory attack, but it’s more of an exploratory action. Unfortunately, for a fragile human, even a small test bite from a powerful shark can be devastating.
The “Yum Yum Yellow” Myth: Deconstructing a Popular Belief
This brings us to one of the most persistent myths in ocean folklore: the “Yum Yum Yellow” theory. The idea is that sharks are specifically and aggressively attracted to the colour yellow. This belief became so widespread that for a time, it influenced the colour choices for life rafts, kayaks, and other water safety equipment.
Where did this idea come from?
The origin is murky, but it likely stems from anecdotal observations. Survival-at-sea equipment was historically coloured bright yellow or orange for a very good reason: to be highly visible to human rescuers in planes or boats. If a person was in the water surrounded by yellow gear and was investigated by a shark, the colour was an easy scapegoat. The U.S. Navy even conducted studies on this during the 1970s to develop safer life vests for downed pilots.
Why is it a myth?
Given that sharks are likely colourblind, they aren’t attracted to yellow because of its “yellowness.” They are attracted to it because, in the visual spectrum, yellow is one of the brightest colours and creates an extremely high contrast against the blue and green hues of the ocean. To a shark’s monochromatic eyes, yellow appears as a very bright, almost white, shape. It is this high visibility, not the colour itself, that draws their attention.
Therefore, any colour that creates a strong silhouette could have the same effect. White, silver, and bright orange would all be perceived similarly. The danger of “Yum Yum Yellow” is not that it’s a preferred flavour, but that it makes you exceptionally easy to spot.
So, What Visuals *Might* Actually Deter a Shark?
If making yourself highly visible is a bad idea, then the logical solution is to either become invisible or to present a visual that sharks actively avoid. This is where modern research has made exciting breakthroughs, moving beyond simple colours into the realm of patterns and biomimicry (imitating nature).
The Power of Black and White Stripes (Banding)
One of the most promising shark deterrents is not a colour, but a pattern: bold, black and white stripes or bands. The theory behind this is rooted in aposematism, a concept in biology where an animal uses warning colours or patterns to signal to predators that it is dangerous, venomous, or unpalatable.
Think of the yellow and black stripes of a bee or the vibrant colours of a poison dart frog. Predators learn to associate these patterns with a negative experience and avoid them. In the marine world, there are numerous examples of this, but one of the most relevant to sharks is the banded sea snake. These snakes are highly venomous, and sharks, through either instinct or learned experience, tend to leave them alone.
Scientists and innovators have hypothesized that by mimicking this “warning” pattern, they could trigger a similar avoidance response in sharks. An Australian company, Shark Attack Mitigation Systems (SAMS), collaborated with researchers from the University of Western Australia to test this theory. They developed wetsuits and surfboard stickers with a specific black and white banding pattern. Their research and testing with live sharks, including Great Whites, yielded promising results: sharks were significantly more hesitant to approach a bait box or a wetsuit clad in this pattern compared to a standard black or grey one. The pattern seems to confuse or signal danger to the shark, causing it to swerve away rather than investigate.
The Invisibility Cloak: The Role of Camouflage
The opposite approach to a warning signal is to disappear entirely. If a shark can’t see you, it can’t bite you. This has led to the development of cryptic or camouflage wetsuits designed specifically for the ocean environment.
These aren’t your typical terrestrial camo patterns of greens and browns. Instead, they use a palette of blues, greys, and greens in disruptive patterns that are designed to do two things:
- Match the Background: The colours are chosen to match the ambient light and colour of the water column, helping the wearer blend in.
- Break Up the Silhouette: The disruptive patterns break up the solid, continuous outline of the human form. This prevents a shark from easily identifying the classic human shape, which can otherwise look strikingly similar to a seal—a primary food source for many large shark species.
By reducing the visual contrast and disrupting the wearer’s outline, these camouflage suits make it much harder for a shark to spot a potential target in the first place, thus reducing the likelihood of an encounter.
A Table of Colours and Their Perceived Effect on Sharks
To summarize these complex ideas, here is a table breaking down different colours and patterns and their likely effect on a shark, based on current scientific understanding.
| Colour / Pattern | Common Theory / Appearance | Scientific Explanation (Based on Contrast) | Potential Effectiveness |
|---|---|---|---|
| Yellow, Orange, White | “Yum Yum Yellow” – Attracts sharks. | These are bright colours that create a very high contrast against the dark water. To a colourblind shark, they appear as a bright, attention-grabbing object. | Poor (Likely to Attract Curiosity). These should generally be avoided unless you want to be seen by human rescuers. |
| Black and White Stripes | Warning Signal – Deters sharks. | Mimics the pattern of unpalatable or venomous sea creatures (aposematism), like the banded sea snake. This may trigger an innate or learned avoidance response in sharks. | Good (Promising Deterrent). Scientific testing has shown this pattern can be effective at deterring investigative approaches. |
| Cryptic Camouflage (Blues/Greens) | Hiding – Makes you invisible. | Uses disruptive patterns and water-matched colours to break up the human silhouette and reduce contrast, making it harder for a shark to see and identify the person. | Good (Effective for Avoidance). A strong strategy to simply not be noticed in the first place. |
| Dark, Matte Colours (Black, Navy, Dark Grey) | Low Profile – Blends in. | These colours create a lower contrast against deep or murky water compared to bright colours. They don’t stand out as much, reducing visibility. | Fair (Better than Brights). A safe, neutral choice, though less sophisticated than targeted camouflage or deterrent patterns. |
| Shiny / Metallic | Attracts sharks. | Flashes of light from shiny jewelry, watches, or dive gear can mimic the glint of light off fish scales, which can trigger a shark’s predatory reflex. | Poor (Likely to Attract Attention). It is highly recommended to remove all shiny objects before entering the water. |
Practical Advice for Swimmers, Surfers, and Divers
While colour and pattern can play a role in mitigating risk, they are just one piece of a much larger safety puzzle. True ocean safety comes from a holistic understanding of shark behaviour. Here are some practical tips that combine our knowledge of shark vision with other crucial factors.
What to Wear and What to Avoid
- AVOID High-Contrast Solids: Steer clear of wetsuits or swimwear that are solid yellow, white, or orange. These make you a highly visible curiosity.
- CONSIDER a Patterned Wetsuit: If you spend a lot of time in shark-prone waters, investing in a wetsuit with either a deterrent banding pattern or a cryptic camouflage pattern is a scientifically-backed choice.
- CHOOSE Dull, Dark Colours: If a patterned suit isn’t an option, the next best thing is a simple, dark, and matte-finished suit (black, dark blue, dark grey).
- REMOVE Shiny Objects: Always take off jewelry, watches, and any other metallic items that could flash in the sunlight and mimic fish scales.
Beyond Colour: Other Critical Safety Factors
Remember, a shark’s senses are far more complex than just vision. They also rely on detecting movement, electrical fields (via their Ampullae of Lorenzini), and pressure changes in the water. Therefore, colour is never the only factor.
- Time of Day: Avoid swimming at dawn, dusk, or night, as these are peak feeding times for many shark species.
- Water Clarity: Be extra cautious in murky or turbid water where visibility is low for both you and the shark, increasing the chance of an accidental encounter.
- Location: Avoid swimming near areas where sharks are known to hunt, such as near seal colonies, steep underwater drop-offs, or near fishing boats where bait and chum are in the water.
- Activity: Avoid excessive, erratic splashing. The low-frequency sounds created can resemble a distressed fish, which is an open invitation for a curious shark. Swim smoothly and deliberately.
- Swim in Groups: Sharks are more likely to approach a solitary individual. Swimming in a group reduces your personal risk.
Conclusion: A Shift in Perspective from Fear to Understanding
So, what colour are sharks scared of? The answer is that they aren’t “scared” of a colour in the way we understand it. The most advanced science tells us that because most sharks are colourblind, their world is one of light, shadow, and contrast. The bright, flashy colours we once feared were attractants are really just big, visible “question marks” for a curious animal.
The future of shark safety doesn’t lie in finding a magical repellent colour, but in smartly applying our knowledge of their biology. The evidence strongly points toward two effective visual strategies: using bold, striped patterns that mimic nature’s own warning signals, or using advanced camouflage to blend seamlessly into the aquatic environment. By shifting our focus from fear to understanding, we can make more informed choices about how we dress and behave in the ocean, fostering a safer and more respectful coexistence with these ancient and vital predators.