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 and steam. Its chemical make-up is a covalent bond of two Hydrogen atoms and one Oxygen. The covalent bond is strong, but the energy released from breaking this bond is low and hard to capture. It is a polar molecule, forming weak Hydrogen bonds between the positive Hydrogen ends and the negative Oxygen end.

Appearances in the Halo Universe

 * Water is seen in plain sight the majority of all games. It appears in 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 (excluding water vapor in a latter form).
 * Frank O'Connor is a self-confessed fan of video game water.

Also See

 * The wikipedia article on water.