Nowadays, as a consequence of the mushrooming growth of photoinduced electron transfer (PET), the water-involved photooxygenation reactions based on unsaturated bonds are becoming manifold and predominant. In this mini-review, we have summarized the recent advances in photochemical transformations using water as an oxygen source since 2020, and highlighted the sustainable feature brought by harnessing the green properties of water in photoreactions. Relevant reports are comprehensively organized by the type of O-containing product targets, including silanols, alcohols, carbonyls, phenols, diaryl ethers, and oxazolines. We hope this review would provide a prospective overview of this topic and stimulate significant research interest.