[Kosh]

In the movies you'd sometimes see someone in the ocean without goggles on and they seemingly can see just fine. My question is in real life if you tried to do something like that, wouldn't it sting your eyes?

[Al Tarket]

nope, your eyes need water in order for them to stay the shape their in. i have swum without googles and looked in water many times before but i dont know what kind of effect it has with long term exposure. on the safe side you should keep your googles on.

for first timers it will be difficult because yours eyes are not used to the amount of pressure water has and the sort of environment its heading into.

[castor]

I'd imagine slightly salty water to be nicer for the eyes than fresh water.
Hmm... salt is cheap, in addition one only needs a bucket to test this out..

[G0atmaster]

slightly salty water.  But the Ocean does sting a bit at first.


Saltwater swimming pools are easier on the eyes than Chlorine swimming pools, though.

[redsniper]

Well, if you've ever been to the beach and gotten seawater in your eyes, you know it burns. Slightly salty water would indeed feel better on your eyes than pure water, but the sea is much saltier than your tears and such, so it would be no fun.

[castor]

but the sea is much saltier than your tears

Hey that'd make a nice proverb
But yeah, sea water saliness appears to be about 3,5% whereas tears are just 0,9%.

[NGTM-1R]

You can, I've done it several times due to defective googles or simply not having them. It stings less then you would think and the visual distortion is actually less than pool water usually (though I couldn't tell you why). However, you will do a lot of crying after you surface because the saltwater has, well, salt in it, and this will try to dry out your eyes. As with cholorinated water, you mainly pay later.

Although, from secondhand experience, do not attempt this below fifty feet, as the pressure may cause damage to your vision. (During my brief flirt with Scuba, my classroom instructor mentioned that he had to wear glasses as he had his googles crack when he was swept into a piece of hull while he was wreck diving at 120 feet or so, the pressure permanently damaged his eyesight.)

[Herra Tohtori]

You can, I've done it several times due to defective googles or simply not having them. It stings less then you would think and the visual distortion is actually less than pool water usually (though I couldn't tell you why). However, you will do a lot of crying after you surface because the saltwater has, well, salt in it, and this will try to dry out your eyes. As with cholorinated water, you mainly pay later.

Although, from secondhand experience, do not attempt this below fifty feet, as the pressure may cause damage to your vision. (During my brief flirt with Scuba, my classroom instructor mentioned that he had to wear glasses as he had his googles crack when he was swept into a piece of hull while he was wreck diving at 120 feet or so, the pressure permanently damaged his eyesight.)

Wat?

Swimming goggles are indeed a bad choice to dive with, since the pressure inside them stays constant (1 atm) and thus the surrounding water tends to press them towards the eyes causing kind of a suction cup effect. But scuba diving mask is a bit different thing; since it has open connection to the airways through nose, the pressure inside the mask is the same as the air that is in your lungs, and the air in your lungs is about the same pressure as the water at that depth... so the mask actually balances the pressure to the surrounding water to avoid the "suction cup" effect of the goggles. So I don't really know what happened to that instructor.

As to the first question, water that has the same salinity as body doesn't sting. With fresh water, the osmosis (diffusion of water through semi-permeable foil like cell wall or the surface of eyes) tries to force some water through the eye's surface to dilute the saltier solution inside; with salty sea water the less saline solution inside the eyes tries to get out to dilute the salt water in sea. Sand, dirt, chlorine and other stuff in the water can cause stinging as well, but that's the basic gist of "why water stings eyes", somewhat simplified.

[NGTM-1R]

Don't ask me. Perhaps he was skindiving. 120's deep for that but not so deep as to be impossible.

[pecenipicek]

bloody eyes rule.

[watsisname]

An important note about the ability to see (clearly) underwater is the fact that our eyes are adapted to viewing through an interface of gel and air, which have notably different densities, thus resulting in a certain amount of refraction.  When we look underwater with unprotected eyes, light is no longer passing from air to gel, but water to gel, thus causing a blurring effect due to a different level of refraction.

As for discomfort, I've looked through oceanwater a few times and it's far less uncomfortable than, say, chlorinated pool-water.

[FUBAR-BDHR]

Probably more nasty stuff in ocean water that you don't want in your eye though.

[G0atmaster]

That makes sense.  I've never thought about the osmosis thing.

I thought that was only true for semipermeable membranes?  As far as I know, the Cornea is not such a membrane (at least as far as water is concerned).

[Mars]

But the outside of your eye is, not the optical part AFAIK, but the white part.

At least that's what I remember from dissecting a sheep's eye

[G0atmaster]

That's what I was talking about.  The Cornea.  The outermost protective layer.  The place blood doesn't even flow to, it's oxygenated by gas absorption.   

The inside of your eye has a fluid called Vitreous Humor.  That's composed mostly of water.  but it sure as heck doesn't seep out.

[Herra Tohtori]

That makes sense.  I've never thought about the osmosis thing.

I thought that was only true for semipermeable membranes?  As far as I know, the Cornea is not such a membrane (at least as far as water is concerned).

The cornea as a whole is not, it's pretty good at keeping the eye at shape as well as innards in the inside, but the outermost cells have cell walls too and the cell walls in general are semipermeable membranes, which makes them somewhat susceptible to osmosis and other physiological and chemical reactions.

You might have noticed that fresh water tends to sting wounds and abrasions of skin too, which is because it gets in direct touch with living tissue rather than the dead, relatively thick layer of skin cells. The fact that the eye's outer surface is living cells is also why having chemicals like acids and bases on eyes is a lot more critical situation than spilling them on skin - on skin they generally need to eat their way through the stratum corneum before having a chance to cause actual damage so you can wash small amounts away, whereas in eyes they have a direct route to vulnerable cellular surface and even small droplets can cause excruciating stinging and some actual damage.

[Mongoose]

All I know is that I can't even stand the sensation of putting eyedrops in my eyes, so opening them in a pool/the ocean is right out.  I'm a goggles wuss all the way.