Water

Water, chemical name dihydrogen monoxide, is a common chemical substance that is essential to all known forms of life. In typical usage, water refers only to its liquid form or state, but the substance also has a solid state, ice, and a gaseous state, water vapor.

Appearances in the Halo Universe

 * Six of the ten levels of Halo: Combat Evolved, nine of Halo 2's levels, and almost all of Halo 3's levels, in some form or another.
 * Mentioned in Halo: Contact Harvest. Private Jenkins drinks it during some of the training exercises, when the company goes on runs, and during breaks.
 * Frankie is a self-confessed fan of video game water.