Is your ‘yum-yum’ swimwear attracting hungry sharks?

4 min


Is this color combo akin to wearing a steak in the Serengeti?

Just when you thought it was safe to go back in the two-piece: Studies suggest that donning certain colored swimsuits in the water could make bathers more susceptible to shark attacks.

Marine biologist Gavin Naylor, who runs International Shark Attack Files (ISAF) at the Florida Museum of Natural History, suggested that yellow is particularly problematic when “juxtaposed with particular patterns against darker colors” such as the ocean, per the BBC.

“It’s the contrast that they can pick up on,” the shark expert explained. In other words, the universal sign for caution could be like ringing an underwater dinner bell.

The apparent link between bright hues and shark bites has even prompted some to dub the color “yum-yum yellow.”

Naylor based his statement on a series of experiments by Australian physiologist Nathan Hart, who examined the retinal profile of different sharks to see what colors they can and can’t perceive, effectively looking at things through a fish-eye lens.

Studies show that sharks are essentially colorblind.

The alleged correlation between bombastic colors like yellow — which is, coincidentally, the standard color of the U.S. Navy’s life preservers — and shark attacks is a talking point that seems to resurface following every human encounter with the ferocious-looking fish.

It will no doubt rear its toothy head again this year after the recent rash of incidents in Long Island, in which a record five people were bitten in two days over the Fourth of July weekend.

A chilling 2021 video from Florida depicting hammerhead sharks circling two women — who were floating on an inflatable yellow raft like a human crostini — would certainly seem to support the theory.

The contrast between bright colors and the ocean is more important than a dazzling hue itself.
Getty Images

Meanwhile, in a 1970s video for the Navy, prominent shark vision scientist Sam Gruber described a spine-tingling air/sea catastrophe, in which the pilots had on orange uniforms while the crew was wearing “green khaki suits.”

“Pilots – to a man – were attacked by sharks, apparently because they were wearing orange suits, while the men in the green suits were left entirely alone,” he declared, per the BBC.

This is surprising given that aforementioned studies by Hart revealed that while sharks have a superhuman sense of smell — great white sharks can detect a drop of blood in a space the size of an Olympic swimming pool — they may be completely colorblind.

Shark eyes possess a single “long-wavelength-sensitive retinal cone,” meaning they essentially see in monochrome, according to Science Daily.

Over half of all shark attacks occur in turbid water.
Getty Images/iStockphoto

However, that lack of color vision doesn’t mean sharks have bad eyesight.

Another study by Hart found that bottom-feeding species, such as the nocturnal Port Jackson shark, have an extreme sensitivity to contrast compared to vertebrate animals.

That ability to distinguish objects is heightened in clear water, which perhaps explains why blue sharks, oceanic whitetips and other pelagic species prefer to hunt near the surface where the light is good.

It’s perhaps also the reason why attacks are more likely to occur in murky water where people and prey are indistinguishable — a phenomenon that’s true for 60% of all incidents recorded by ISAF, according to Naylor.

Scientists believe that was the case for the shellfish diver who was decapitated by a 19-foot great white shark in Mexico earlier this year.

“If sharks are excited and hungry, they make rash decisions and bite what — in the heat of the moment — they consider a potential prey item,” said the marine biologist. He added that “predators have to think quickly” as hesitation “can leave them hungry.”

“Divers and swimmers can probably reduce the chance of an interaction with a shark by avoiding bright and highly contrasting swimwear or dive gear,” the International Shark Attack File warns. “We personally prefer to use dark blue or black fins, mask, tank, and wetsuit while diving.”
Getty Images/iStockphoto

As for whether vibrant colors actually cause sharks to see red, Naylor determined that certain color combos are easier to detect underwater, even for these allegedly colorblind predators.

“If you’ve got some pattern, like a Secchi disk [for measuring water turbidity], for example, which is black and white, you have a much better chance of seeing it at a distance than if it was in camo greens and yellows,” he explains.

Essentially, it’s not about bright colors but rather how those pigments are juxtaposed against the ocean.

A Caribbean reef shark.

As such, ISAF advises swimmers to avoid “bright and highly contrasting swimwear or dive gear,” adding that they “personally prefer to use dark blue or black fins, mask, tank, and wetsuit while diving.”

Meanwhile, Naylor warns people against wearing watches and shiny jewelry, as this can resemble fish scales when it catches the light, potentially attracting sharks — and even barracudas.

But don’t that doesn’t mean one should avoid wearing a bright yellow life jacket again, as “the benefit of increasing one’s chances of being rescued far outweighs the minimal risk of attracting a shark,” ISAF says.

Not to mention that there is no “one-size-fits-all” clothing rule for deterring shark attacks.

Research by expert Sam Gruber found that lemon sharks are more sensitive to yellow during the day but perceive more green in the evening, the BBC reported.

Meanwhile, swapping bright-colored surfboards for duller ones — a trend among surfers amid the spike in shark attacks — isn’t fool-proof given that great whites, which ambush prey from below, will still be able to see the board’s silhouette.

Nonetheless, perhaps it’s prudent to think twice before donning banana jammies or an itsy-bitsy yellow polka-dot bikini when entering shark-infested waters.

No word as to how color perception would be affected in “cocaine sharks,” which were suspected of feasting on bales of the stimulant dropped by smugglers off the U.S. coast.

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