Underwater River.
If you are a professional diver you should visit Cenote Angelita, Mexico.
There's some kind of cave. When you go deeper than 30 meters the water is fresh, deeper than 60 - it's salty.
And then you see a river underneath, with trees and leaves.
But of course, it's not a real river.
It's just a layer of hydrogen sulphide.
But it looks amazing.
Underwater River in Mexico (4 pics + video) AcidCow.com - videos, pictures, celebs, flash games