THIS is the brainteaser that challenges you to put on your sea legs and find the hidden envelope on the ship.

Everyone can spot the poor souls tied to the mast of the boat, but only those with 20/20 vision and a high IQ can spot the envelope in 18 seconds.

The puzzle will remind you why you get seasick as the rickety-looking vessel braves the rough seas.

Hopefully the captives have a plan to get out of this dangerous situation.

What makes this teaser difficult is the dull colours of brown and blue, making it hard to differentiate different objects in the frame.

It makes it hard to solve because the block colours don’t give you much to pick out.

It may sound tough, but the key is to focus on the shape of the envelope rather than the colour of it.

Are you ready, because there’s turbulent waves up ahead and you need to brace for impact!

If you find yourself struggling, a hint would be to pay attention to the outside of the boat.

People who are able to solve the puzzle quickly possess good observational skills and high cognitive speed.

It tests your ability to process a high volume of visual information and the ability to concentrate under high amounts of pressure.

Psychologists at The University of Glasgow found that staring at an optical illusion can improve eye sight by allowing you to see small print.

Escape London says puzzles can also give your mind a great workout and may “boost your brain’s activity” which “reduces the risk of dementia.”

These can help to stimulate several parts of the brain at the same time.

Tasks like this can also provide people with a productive way to have fun and relax.

Have you solved it? Don’t worry, if you’re still struggling we’ve included the solution to the brainteaser down below.

Why not see how many hidden items you can find in this airport scene in just 22 seconds?

Or see if you have the eyes of a hawk by trying to find the sailor’s wife in this illusion.

If you’ve solved those, why not try out some more optical illusions down below?