I can not "use" bucket on aquatic mobs. Action is ignored. I can attack the mob. Other "use" actions work properly (i.e. fill bucket with water).

As a side note, that may be related or perhaps a new rule, I can no longer empty a bucket of water on a water background alone, there must be a solid block target to use the bucket.

I have attempted the action on a stand alone game, a private server, a Realm server, with a PC and an Android tablet and on multiple worlds.