Use plugin with this code:

@EventHandler (priority = EventPriority.LOW)
public void playerBucketEntityEvent(PlayerInteractEntityEvent theEvent) {
    theEvent.setCancelled(true);
}

Then spawn axolotl in water and try to catch it using water bucket. Axolotl disappears on client side, but it's still exists on server side (also visible for other players) and it's easy to see this by looking at the subtitles.

This issue doesn't exist if we use PlayerBucketEntityEvent instead