Summary:
When submerged in lava, sprinting will cause the player to swim in the lava, but in a buggy way. The player's paper doll seems to repeatedly move up and down very fast and the fire in first-person view shakes/flashes violently, depending on which way you're looking. The fire will also frequently become off-centered.

Steps to Reproduce:

1. Make sure "Hide Paper Doll" is off.
2. Be in Creative mode.
3. Submerge yourself in a deep pool of lava.
4. Start sprinting.

Observed Results:
The player's paper doll repeatedly moves up and down very fast and the fire in first-person view shakes/flashes violently.

Expected Results:
The player just sprints in the lava and nothing else happens.