THIS optical illusion has been stumping even the most hawk-eyed of puzzle fans.
You might just have 20/20 vision if you can spot the shark in this seemingly serene picture of the sea.
Yes, there really is a shark in there.
For those puzzle-heads among you, there's an added catch: you have to try and find the shark within 11 seconds.
So, grab a timer, set it to 11 seconds, and prove your puzzle-solving abilities.
Although it may seem like an ordinary image, this is no easy feat and 99 per cent of people fail to find the shark.
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Facebook user Linton Allen shared the picture to Facebook after he realised the sinister being lurking below the surface.
If you look closely, you might be able to spot it too.
Optical illusions are purposefully designed to trick our vision, and can be used as simple determiners of intelligence.
Optical illusions benefits
RESEARCHERS have developed many tests that show how various brain regions react to optical illusions.
They are not only entertaining, but they also shed light on how our brains interpret visual data.
By giving your brain a little workout on a regular basis, you enhance your ability to focus and observe details.
Studies have shown, people who regularly challenge themselves with optical illusions and puzzles see big improvements in their problem-solving skills, concentration and attention.
Improved concentration and attention span, in turn, can help prevent cognitive decline in older age.
Psychologists at The University of Glasgow found that staring at an optical illusion can improve eyesight by allowing you to see small print.
The pic was shared on the Dorsal Perth Shark Reports page and several followers jumped at the chance to give the optical illusion a go.
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One user commented: "That is way too close to shore for my liking!"
Another added: "Looks like a toona (sic) fish."
While a third simply said: "Sheesh!"
Have you found the shark yet?
If you'd like some help, try breaking the image down into several sections. Then search each section slowly, one at a time.
Or, if you found this puzzle too easy, try some of our other brainteasers.
Can you find all four animals lurking in the shoreline in this image?
The catch is, you only have five seconds to find them all.
It's considered so hard that only two per cent of Brits can actually complete it in time.
What about this image of tend red cars in a row?
Onlookers are being told they have an incredibly high IQ if they can find the odd car in just 10 seconds.
We've also added three bonus puzzles at the end of this article for you.
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But, have you found the sneaky shark yet?
If you couldn't find it within 11 seconds, don't worry, we have the answer for you.