Under the correct circumstances, the player's legs and body appears to shake and arms appear to "row" when in a boat

1. Generate a superflat world with 64 layers.
2. Place 1 full block.
3. Put a boat on it.
4. Press F5 twice.
5. Your arms will be moving up and down.
6. Rotate the screen to make this affect will happen.

Note: This does not occur in 1.7.10
I'm not sure why, but every time I see it I laugh.