Chop the plums into small pieces about 1.5 inches by 1.5 inches. Remove the pit, but leave the skin on.
Add the water, sugar and chopped plums to a large pot. Mix well. Bring to a boil, then reduce to low heat.
Cook for 12-14 minutes, stirring frequently or until the plums are soft and can be smashed with a spoon. Remove from heat and allow to sit for 5 minutes.
Pour the plum juice mixture into a large blender or food processor. Blend until smooth.
Use a fine mesh or a cheese cloth to strain out any excess pulp, skin or large pieces. Add extra water to reach desired flavor and consistency.
Transfer to a large bottle and refrigerate. Serve cold.