Why when we look at water it’s clear. but when we go under water it’s blurry?

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Why when we look at water it’s clear. but when we go under water it’s blurry?

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The proper function of our eyes depends on there being air on the outside of our eye’s lens. The shape of our eye, the lens, cornea etc. are all designed to focus light very precisely on the retina at the back of our eyes.

When you are near or far sighted and need glasses or some other type of correction, its because, for one or more of some very good reasons (age, growth, atrophy and their derivative conditions: glaucoma, lens stiffness, eye shape, whatever etc.) the light isn’t being focused in the right spot.

Refraction is where light _bends_ as it transitions between two different but still transparent (or light carrying) materials. You can see this when you put a straw into a glass of water – above the water its at a certain angle, below, its at a different angle (or so it would seem, as you look at it from above the glass).

The shape of our eyes, the lens in particular, has evolved to focus the incoming light on our retinas accounting for the refraction between air and the material of our eye’s lenses (and then the clear goo that fills our eyeballs). If you replace the air with water, that amount of refraction goes bork and the light you see through your eyeballs is no longer focusing quite in the right spot.

Having said that, I bet some – very few – people who DO need corrective eye-wear out of water, might actually be able to see _better_ underwater. But I’m not an optometrist so I’m speculating.

Your eyes work best when coupled to air. They transfer function does not work well when they are coupled to water.

This is why you can see clearly with a face mask filled with air over your eyes.

Human eyes can’t work properly under water, they’re not made for that, and the way light behaves in air and in water is different, but our eyes have no way to adjust to that. When you’re looking at water your eyes are not submerged, so you just see the water as the liquid it is, with all its quirks related to light like refraction and such. But when you actually submerge your eyes under water then the water is not any less clearer, it’s just that your eyes can’t actually adjust for the distortions the water causes to the light.