Water is breathable?

I was exploring on one of my survival worlds in the newest snapshot when I realized I had run out of stone, and I needed some for a pickaxe or something. So I looked for the most easily accessible stone and found some on the side of a lake. After finally breaking enough stone to get a hole to breathe in, I accidentally broke a sandstone block, which let down some sand.

For whatever reason I decided to break the sand, which let in some water, creating a water source where I had gotten my "breathing hole" in, which I expected. Then, after blocking off the water, expecting the water to leave the spot, I noticed something off. I could breathe where the water was.

What I expected to happen was...:
I would start to lose air and have to make another air hole.

What actually happened was...:
I didn't start drowning when I should have.

Steps to Reproduce:
I'm not good with text instructions, so watch this recording I made of it instead.

I'm also going to include my initial recording too

How-To Video

Initial Video