Swimmers afraid of sharks might be best off in swimming costumes that camouflage their bodies rather than in ones with bright, solid colours that emphasise their outline, Australian researchers said Wednesday.

Sharks, like dolphins, seals and whales, are most likely colour blind and see things most clearly if they are mostly light or mostly dark, researchers from the University of Western Australia (UWA) and the University of Queensland found.

“It’s the high contrast against the water rather than the colour itself which is probably attractive to sharks,” UWA associate professor Nathan Hart told national broadcaster ABC in Perth. “So you should wear perhaps more muted colours or colours that match the background in the water better.” Even better would be a wetsuit with zebra stripes or a leopard print pattern.

The researchers examined the eyes of dead sharks and found they had only one type of photoreceptor in the retina, indicating they could only see in monochrome. Humans, and most other fish, have several types, allowing them to distinguish between colours. Hart said that the US Navy had conducted tests that suggested sharks were able to see yellow most clearly. The tests had been to see what would be the best colour for the lifejackets that pilots wear in case they have to eject and splash down in the ocean.

Hart said it was more the high contrast of yellow, not the colour itself, that would increase the visibility for sharks.

“It may be possible to design swimming attire and surf craft that have a lower visual contrast to sharks and are therefore less attractive to them,” Hart said.

Lindy Woodrow, a Sydney resident and keen ocean swimmer, said far more people drowned than were attacked by sharks and that although camouflaged costumes might mitigate against shark attacks, the primary concern for most would always be visibility in the water.

“What’s most important for me is that people can see me so I can get rescued if I get into trouble,” she said. “I always wear a bright costume and a fluorescent swimming cap.” The research paper is to be published in the German nature journal Naturwissenschaften — the Science of Nature.