To wash your water-resistant beach bag, start by emptying it of all contents. Wipe down the exterior with a damp cloth to remove any surface dirt or sand. For deeper cleaning, use a mild soap or detergent mixed with water and a soft-bristled brush to scrub the fabric gently. Rinse thoroughly with clean water and allow it to air dry completely before using it again. Avoid machine washing or using harsh chemicals to preserve the bag's water-resistant properties.