What I expected to happen was...:
I tought after death everything would go back to normal, but it didnt.

What actually happened was...:
What happend was that drowned became invisible and i couldnt attack them or defend myself, and they appeared again after respawn, and this happend every other time. in this world i had worldspawn right beside the drowned.

Steps to Reproduce:
1. find a drowned village or any drowned mob, and attack it,
2. die from the drowned or a trident from a drowned,
3. respawn and try to kill the drowned but this time they are invisible, and then if you die and respawn again they appear visible again.  

hope this helps!