Do Sharks See Color? Why Your Swimsuit Color Doesn't Matter

Picture this: hundreds of men stranded at sea in the wreckage of their ship. As they cling to the refuge, waiting for rescue, one by one, they begin getting picked off by sharks.

Curiously, the tale goes, every man taken to his watery grave had one thing in common — they were all wearing orange pilot suits. All the men dressed in green khaki suits were left alone.

Samuel Gruber, a shark biologist, recalled this anecdote in a 1970s US Navy documentary about shark behavior. He said that story is the reason the Navy sponsored his research into shark vision, in an effort to determine why sharks seemed to be provoked by certain colors.

This is a popular story in shark communities and is likely the origin of the myth that shark attacks may be caused by wearing bright colors, like yellow or orange. People even dubbed it "yum-yum yellow."

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Sharks can't see color very well

Though Gruber's 1977 work confirmed sharks have sharp vision, it stopped short of drawing conclusions about color. But the more that modern research peers into the eyes of sharks, the less support there seems to be for the theory that sharks prefer to bite people wearing yellow or orange swimsuits. 

A 2020 review of all the data to date said that most species of the predatory fish can't even see color.

Most sharks only have one type of cone, which are the cells in eyes that pick up color. Most humans, by contrast, have three types of cones. This allows us to be sensitive to a whole range of colors in the visible light spectrum.

But because sharks only have one type of the cell, they can only see in shades of black, white, and gray, the review reported.

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Even with this limited palette, the sharks are extra sensitive to differences between colors because their eyes are sensitive to light. This also clues them in to how vibrant a color is, according to the University of Florida's international shark file. 

So when it comes to swimmers wearing bright colors, it's not the shade that sharks see, but "it's the contrast that they can pick up on," Gavin Naylor, director of the University of Florida's Program for Shark Research, told the BBC.

Sharks may be attracted by contrasting colors

Nathan Hart, who authored the 2020 review, stated that contrast may be the attribute attracting the sharks.

So, it isn't one specific color that attracts sharks, but they may be able to better see people in bright colors because it's a stark contrast to their blue, watery surroundings. 

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This may make it easier for them to spot you. And if on the off chance, they're in the mood, easier to attack. 

This sensitivity to light and ability to see the difference between two colors likely evolved so that the sharks could live and hunt in deep, dark waters and at twilight, Hart said in his paper. 

Keeping all this in mind, authorities on the subject say you can switch out your swim trunks if you want, but it may not be a perfect solution. Yellow and orange are the best colors to wear if you end up in a dangerous situation and want to be spotted by rescuers. 

"There is a trade-off involved, but most would agree that the benefit of increasing one's chances of being rescued far outweighs the minimal risk of attracting a shark," Florida's International Shark File detailed.

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