You can breath underwater in non source blocks of water

when I start diving in a 2 blocks of height lake in which I have broken the layer of sand to make it 2 blocks and start diving in the newly created area it doesn't show the breath bubbles like I'd be at the surfaces (the bubbles regenerate in that area) 

P.S. The video file size was too large to put it directly here so here is a youtube link: https://youtu.be/FlrNbPW7ax8