Hm. Salt water is (according to my google-fu) denser than fresh water. The article says, "When the eye is immersed in water, which has about the same density as the cornea, we lose the refractive power of the cornea..."

I wonder if this refers to salt or fresh water. Maybe both, if the density delta between the two is trivial.

I know, but the crux of the article seems to be that you shouldn't be able to see underwater even if you can keep your eyes open. I could/can see underwater just fine but only if I can keep my eyes open of course. I cannot keep my eyes open in salt water, but that might be a lack of acclimatization is what I'm saying.