Place cantaloupe, 1 1/2 cups water, lime juice, and measured sugar in blender and blend on high speed until smooth, about 20 seconds.
Strain through fine-mesh strainer set over large pitcher or bowl, using ladle or wooden spoon to press down on solids (should have about 2 cups of liquid). Discard solids.
Add remaining 1 1/2 cups water and stir to combine. Taste and add additional sugar as needed. Refrigerate until cold, at least 1 hour. Serve over ice.