This underwater river there in cenote Angelita, Mexico. There is a cave that if dived to a depth of 30 meters, the water is freshwater, but if you dive to a depth of more than 60 meters, the water becomes salt water. At bottom there is a "river" complete with trees and foliage. But, of course it was not unusual because the river is a river of hydrogen sulfide layer that looks like a river.
If you just look at the photos probably will not believe it ... try to watch The video below ..
