Use a sharp knife and cutting board to peel and slice the cucumber into thin rounds.
4 cups watermelon flesh, cubed
Place the watermelon flesh cubes into the blender and add the sliced cucumber. Blend on high speed until smooth and uniformly puréed, about 30 seconds.
4 cups watermelon flesh, cubed
Pour the blended mixture through a fine mesh strainer or nut milk bag positioned over a glass pitcher or bowl. Use a spoon or spatula to gently press and extract the maximum liquid, discarding the pulp
If desired, add finely chopped fresh herbs into the extracted juice for earthiness and aromatics. Stir gently to combine.
4 cups watermelon flesh, cubed
Pour the finished juice into chilled glasses, garnish with additional herbs if desired, and serve immediately for maximum freshness and flavor.