The specific color of a bathing suit is a common concern for ocean swimmers seeking to minimize risk. While color does play a role in visibility, the science behind shark perception is often misunderstood. The effectiveness of a swimsuit color is not about the hue itself, but rather how it contrasts with the surrounding blue or green water. Understanding how light travels underwater and how sharks process visual information provides a more accurate basis for choosing swimwear.
How Sharks Perceive the Visual Spectrum
The visual system of a shark is fundamentally different from that of a human, focusing less on the color spectrum and more on light sensitivity and contrast. Scientific studies suggest that many shark species are monochromatic or dichromatic, meaning they see the world largely in shades of gray, or with a limited perception of color. Their retinas contain a high density of rod cells, which are optimized for detecting movement and light intensity, particularly in low-light conditions. This adaptation gives them excellent vision in dim, murky, or deep waters, but it prioritizes contrast over true color recognition.
The way light behaves in water further limits the significance of color. Water quickly absorbs longer wavelengths of light, such as red and orange. Blue and green light, which have shorter wavelengths, penetrate the deepest and are scattered throughout the water column. Consequently, the ocean environment is naturally dominated by a blue-green background, which means any object not in that spectrum will stand out dramatically. A shark’s visual acuity is therefore tuned to detect silhouettes and sharp outlines against this pervasive blue backdrop.
Color Choices That Increase or Decrease Visibility
Given the shark’s reliance on contrast, the colors to avoid are those that create a stark outline against the water. Bright colors like yellow, orange, and white are particularly noticeable because they contrast sharply with the blue-green ocean tones. This high-contrast effect is why yellow gear has earned the nickname “yum-yum yellow,” as it is easily distinguishable to a shark, even if they do not perceive the color yellow as a human would.
Even dark colors like red can increase visibility in deeper water. This is not because the shark sees the color red, but because red light is absorbed quickly, causing the object to appear dark or black. This creates a highly contrasting silhouette against the lighter surface water above. Therefore, for minimal visibility, the safest colors are those that blend into the environment, such as deep blue, navy, or dark gray.
Any reflective or metallic material should also be avoided, as these accessories can produce sudden flashes of light underwater. These glints mimic the flash of light reflecting off fish scales, which can be interpreted by a shark as a potential food source. Items like shiny jewelry, watches, or goggles with mirrored lenses can increase the likelihood of drawing unwanted attention.
Factors That Influence Shark Encounters More Than Color
While swimsuit color is a simple variable to control, it is a minor factor compared to environmental and behavioral elements that influence shark encounters. Erratic, splashing movements on the surface create low-frequency vibrations in the water that sharks are highly adapted to detect through their lateral line system. This kind of choppy movement can mimic the distress signal of an injured animal, which is far more attractive to a predator than a static color.
Location and time of day are significant determinants of risk. Swimming in murky water or near river mouths, where visibility is low and prey items gather, increases the chance of an encounter. Dawn and dusk are considered higher-risk times because low light conditions compromise the shark’s vision, increasing the chance of a mistaken identity investigation.
Proximity to fishing activity or areas with high concentrations of natural prey, such as seal colonies, significantly elevates the risk regardless of the clothing worn. These environmental and behavioral factors are the primary drivers of a shark’s interest.