When swimming underwater in an uncovered body of water, if a player punches a mob and keeps swimming, they do not need to fully surface.

What I expected to happen was...:

That the air meter would keep going down, despite having punched a mob.

What actually happened was...:

The air meter increases when underwater by one block. Air also increases momentarily when going from one block underwater to increased depths.

Steps to Reproduce:
1. Get an uncovered body of water and swim in it.
2. Punch a mob and keep swimming.
3. Swim to one block depth in water, and then also deeper.