Able to breath under flowing water

I was digging into the side of an underwater hill, when I realized I could breath underwater, as long as it was flowing water.

The image that was taken during the day only has 1 water source block, which is directly above my head. All the flowing water (incl. under it) is breathable!

 

P.S. I had to upload screenshots after I posted this, because it was telling me it was "missing a token".