Re: How salty is the ocean?

The scientific word for saltiness is salinity. The average salinity is 3.5%. 
Your body has salt in it, too. The salinity of blood is 0.9%, so the sea has 
about 4 times the salinity of blood. It is thought that at one time the oceans 
were less salty and that life developed at a time when the ocean salinity was 
much closer to 0.9%.

Now, whether 3.5% salt concentration is a strong enough to hurt your eyes is 
something I am not so sure about. At the beach there are a lot of things that 
could cause eye irritation. Probably the most common is sunlight. The corneas 
of your eyes can get sunburned. The sand and water reflect a lot of the 
ultraviolet rays, so there is a greater exposure at the beach. It usually takes 
a couple of days to recover from that injury. It is called solar keratitis. If 
you look at your eyes when that has happened you will see what's called a flare 
around the the limbus. That is where the whites of the eyes meet the colored 
iris. Sand and things floating in the water can also be sources of eye injury. 
If those are the sources of the irritation, you would see the whites of the 
eyes being uniformly red.

David.