Enzymes are complex structures that have been produced by evolution to function in water. The interrelation between water and proteins is not completely understood. However, data of the last decades have shown that water is indeed an essential component of enzymes. It is central in their formation, often it forms an essential part of their three‐dimensional structure, and it is fundamental for supporting enzyme action, at least at rates compatible with life. It is precisely because of the intimate relation that exists between water and enzymes that water may be used to gain deeper insight into how enzymes are formed and function.