Add the sliced cucumber and cold water to a pitcher.
Refrigerate for at least 1 hour before serving. If desired, gently mash the cucumber slices with a wooden spoon to release more flavor.
Serve chilled. Store in the refrigerator for up to 3 days.
Notes
Cucumber water is best served the same day but can be stored covered in the refrigerator for up to 3 days.For additional flavor, add fresh lemon slices or mint. Sparkling water can also be used in place of some or all of the still water.