My son is six months. Can I feed him Gerber cereal with baby water?

"Baby water" is only an excuse to charge more money. Regular bottled water is fine, better yet use tap water(unless its contaminated) Typically you mix with formula or breast milk because it gives the bland cereal some taste and makes them more likely to want to eat it. Try about a tablespoon, when he can eat that fine give him another tablespoon