The bug
When player is swimming animation in third person, switch to first person and leave water. Player's arm in first person isn't on screen but still see when breaking block (See like arm is far back from normal). Switch to third person, open GUI bring player's arm back.
How to reproduce
Swimming in third person mode
Still swimming, but switch back to first person mode. You will see player hand is missing.
Leave water
→ ❌ Notice the missing arm
I was reporting another bug and I stumbled in this animation bug. Virtually the arm is not missing, but the animation stops when you switch from third to first person while leaving water.