Upon being submerged when your head is about half way in the water in first person, you are able to see through the waters layer. See photo attached.

Steps to reproduce

• Find an ocean or a lake that is at least 5 blocks deep.
• Go into the water and use up/down arrows.
• Just before completely going underwater you should be able to see or briefly see through the waters layer.

I attached a world save with the player at this current position.
When you open the world don't use the fly arrows, make sure you look up and down and you will see that there is no water layer.