Will it flood my caves and house? If so, I need to seal them up..
Edit: Nice church!
No, but you should seal them up when you get a chance.
I will run a basic algorithm that attempts to remove voids in the water because it's griefed all over the place. It will look for air blocks with 3 or more water blocks next to them.
After that, water blocks (at least below sea level for sure) will be unclickable... but you will be able to place blocks in water. If you remove a block that borders water then it will fill with water... but this will not "flow".
It's just enough water fixing to prevent the random griefing that happens.