I figured out how to get Lightning AND Water into one spell despite them being opposites, but I have strong feelings this is a bug, so I don't do it.
Create Steam, then Lightning, and use Cold to eliminate the Fire in Steam to make Water.
OR
Create Ice, then Lightning, and use Fire to eliminate the Cold in Ice to make Water.
Create Steam, then Lightning, and use Cold to eliminate the Fire in Steam to make Water.
OR
Create Ice, then Lightning, and use Fire to eliminate the Cold in Ice to make Water.