We have recently studied the intereaction of adsorbed water with oxygen adatoms on the Au(111) surface and, additionally, the reactions of these co-adsorbates with gas-phase carbon monoxide. Water interacts strongly with adsorbed oxygen atoms on Au(111) making hydroxyl groups which randomize upon annealing as shown via temperature programmed desorption measurements (TPD). In TPD spectra we observe mixing of the oxygen in overlayers of water (with labelled oxygen 18) and atomic oxygen in both water TPD spectra as well as oxygen TPD spectra. These co-adsorbates also oxidize CO very readily at temperatures as low as 77K. Atomic oxygen reacts with gas-phase CO on Au(111) but adsorbed water alone does not. We speculate that adsorbed hydroxyl [from the interaction of atomic oxygen and adsorbed water] reacts readily with gas-phase CO since we observe more product in the oxidation of CO when water is co-adsorbed with atomic oxygen than with atomic oxygen alone. DFT calculations have been performed which support the experimental findings.