I have been playing Minecraft killing monsters when I had an issue. I was being attacked by invisible mobs such as skeletons, spiders, zombies and creepers. Sometimes when I was able to locate these mobs, I was unable to hit them. This means that I experience arrows shooting at me from different places and random explosions and attacks. On the water issue, occasionally when I pick up water with a bucket, it shows that my bucket is filled with water and the water source block is disappeared. However, when I place down that bucket, the water shows for a while and disappears. And when I go back to the original water source, I cannot see the source block but I can see water flowing from the invisible block. I hope you can fix these issues.