Something Just Did Not Seem Right About Theses Pictures,

to us it seemed like the diver had been Photoshoped in,

but no these pictures and many more taken by photographs by Anatoly Beloshchin tell the story of a hidden underwater river in in Mexico’s Yucatan Peninsula called Cenote Angelita or 'Little Angel', the river itself is actually a sort of illusion due to a phenomenon called a halocline, where waters with different levels of salinity form into layers because of a variation in density,

according to Beloshchin, Cenote Angelita is comprised of fresh water until about 29 meters when it switches to a 1-meter layer of hydrogen sulfide, after which the entire cave bottom is filled with saltwater from 30 to 60 meters deep, so in reality the 'river' is actually just a dense layer of saltwater resting at the bottom of a cave, but apart from all of that what great out of world almost photographs, as an aside if you are into underwater caves have a look here at some more here.