Graphene oxide (GO) is a potential precursor for the bulk production of graphene as the synthetic route is simple and cost-effective. Typically, reduction of GO is a time-consuming process and involves either toxic/hazardous reducing agents or high temperature treatment. Herein, we report the role of intercalated water and thickness of GO films towards the reduction of GO employing simple camera flash. A fast, simple and single camera flash instantaneously causes the deoxygenation reaction of GO without employing hazardous/toxic chemical reductants at room temperature. Successful reduction of GO employing camera flash has been verified via XRD, Raman and UV-vis spectroscopic analyses. Flash-reduced graphene shows a relatively high conductivity value of 740 S m(-1) with a C/O ratio of around 9.5. Intercalated water molecules facilitate the reduction by electron-hole pair formation. It has also been found that the intercalated water facilitates the reduction of GO up to a certain film thickness. However, the intensity of light passing through to the backside of a too thick film decreases significantly, causing incomplete reduction.