When entering or leaving swimming mode both arms now move parallel instead of symmetrical

The bug

The animation for entering and for leaving the swimming mode looks weird in 1.16 pre-release 5. The arms no longer move symmetrical. They now move parallel.

How to reproduce:

1. Go into water
2. Switch to 3rd person mode
3. Enter and leave simming mode

It will look weird. One arm even moves inside your body.