The interaction between polymers and water has been a key focus in science and technology for centuries. The study of polymer–water interactions has early roots in practical, hands-on observations rather than scientific discoveries. Ancient civilizations, such as Egyptians and Mesopotamians, were among the first to use natural polymers like gum Arabic and plant resins. These natural polymers were used in water storage and purification long before they understood the science behind it. As scientific inquiry progressed, especially during the seventeenth and eighteenth centuries, pioneers like Robert Hooke and Anton van Leeuwenhoek began exploring materials with polymer-like behaviors in water. In the mid-nineteenth century, Thomas Graham systematically studied how substances like gelatin interact with water. His work explored how materials dissolve, disperse, or form gels in water, advancing the understanding of colloid chemistry and the behavior of large molecules in solvents. A breakthrough came in 1920 when Hermann Staudinger introduced the concept of polymers as long chains of repeating molecular units. This transformed the way scientists understood their behavior in water and other solvents. This chapter traces the journey from ancient empirical knowledge to the early scientific discoveries that laid the foundation for today’s innovations in water treatment and polymer science. By reflecting on these milestones, we build a clear and engaging narrative of how polymer–water interactions are understood through observation, experimentation, and discovery.