Start by cutting the watermelon into small chunks, removing the rind and seeds.
Place the watermelon chunks into a blender or food processor.
Add the fresh mint leaves and lime juice to the blender.
Blend the ingredients until you achieve a smooth consistency.
Strain the mixture to remove any pulp or seeds.
Chill the watermelon water in the refrigerator for at least an hour.
When ready to serve, pour the watermelon water into glasses filled with ice cubes.
Garnish with a sprig of fresh mint or a slice of lime, if desired.