You can't get out of lava

Put the summary of the bug you're having here

What I expected to happen was...:
For my player to be able to swim/jump out of a 1 block deep pit of lava on creative
What actually happened was...:
I tried swimming/jumping out of the lava pit, but i could't get out.

Steps to Reproduce:
1. Go into a creative world
2. Build a 1 block deep pit of lava
3. Go into the pit of lava and try getting out without flying as if you were in survival