And, that leads to a second question, if it feeds on carbon dioxide, why would water cause it to grow? Water is dihydrogen monoxide. No carbon in water, just two hydrogen atoms and one oxygen atom.

Carbon dioxide is one carbon atom and two oxygen atoms.

So, if this new fire were to need carbon dioxide as opposed to oxygen, then it would need the carbon. Since dihydrogen monoxide does not have carbon, it should not be able to feed the fire and cause it to grow.

A more likely explanation would be if the water itself were to become the oxidizing agent. A fire is a rapid chemical reaction involving an exchange of oxygen. Normally, water would not be an oxidizing agent, because it is relatively stable compared to other compounds. But, with the elemental form of sodium (i.e., “raw” sodium), water (air, too) can serve as the oxidizing agent. Sodium has to be stored in an oxygen free environment, and that includes a moisture free environment, because NaOH is a stronger molecular bond and attraction than H2O. So, when elemental sodium (Na) is exposed to water (H2O), the water molecule will split, with the oxygen atom and on hydrogen atom combining with a sodium atom to form sodium hydroxide (lye) and leaving the remaining hydrogen atom on its own to form hydrogen gas.

So, possibly, you could have used a sodium-based fire, where spraying the fire with water only increased the fire. But, then you would have to explain how the fire maintained its source of sodium.