To clean water stains on marble, choose a cleaning agent suitable for its type and finish. Mild detergents or baking soda paste are safe options. Gather essential tools like cloths, sponges, and brushes. Use gentle materials to avoid scratches. Identify the type of water stain, such as hard water stains or etch marks, and adjust the cleaning method accordingly. Test cleaning agents in an inconspicuous area before applying them more broadly. Blot up spills and use coasters to prevent future stains. Sealers can enhance stain resistance, but regular maintenance is crucial.