Is water a chemical?

Sure, water is a chemical, and sometimes a highly reactive one. It's not apparent because we have adapted to it and even rely on its chemical reactivity.

We are just adapted to water so that its chemical activity is not apparent to us. We take for granted that water is in fact a chemical that participates in the breakdown of starches to sugar and proteins to amino acids (which are then reassembled in the body to make new proteins). We literally cannot live without the chemical reactivity of water. No wonder astronomers who look for life elsewhere are interested in finding water.

Likewise, water is very much a chemical, for instance, in the weathering of rocks where it effectively catalyzes the reaction of carbon dioxide with some minerals (by forming an acid with the carbon dioxide). This, too, can promote life by making essential minerals available to organisms. Simmilarly, water together with other chemicals (oxygen, salts) promotes the corrosion of metals.

Yes, water is a chemical -- and in some settings, a highly reactive one.