The bug
When you are swimming on the ground in water and look down (The vertical direction you are looking must be positive), you will stay in swimming mode even when stopping moving. This does only happen when you are on the ground and looking down.
How to reproduce:
Swim with the swimming animation in water down to the ground
Look down
Stop moving
❌ You will stay in the swimming animation.
Expected result: You will stop swimming. You will only stay in swimming mode, when a block is above you.
Attachments
Comments 2
was introduced in 18w07a (https://www.minecraft.net/en-us/article/minecraft-snapshot-18w07a in this snapshot the ability to swim with the swimming animation was added)
I can confirm for 1.16.3