When experimenting with the wither and conduits, the wither showed block breaking particles when taking damage from the conduits when underwater. Further investigation showed that it does this when taking (melee) damage too.

What I expected to happen was...:

Not seeing block breaking particles when the wither is underwater.

What actually happened was...:

Even when not breaking 'blocks' but 'water' it showed block breaking particles using the water colour (shown in the screenshot) and played the block breaking sound.

Steps to Reproduce:

(all steps below are executed in gamemode creative)

1. Spawn a whiter above water.

2. Let the wither dive into the water.

3. Punch the wither (apply (melee) damage).