This will lag your game, make your world unusable, and is not revertible. BE CAREFUL!
It will literally cover your world in water, so you should probably make a new world for this if you want to use it at all.
Have Fun!
(Hint: To speed up the process and possibly lag your game even further, do /execute @e ~ ~5 ~ /summon Squid)
PS: I might be able to create a command that fixes the damage, and if I do it will be called Water World Clean Up.