In a blender, puree blueberries with water, sugar, and fresh lemon juice. Strain mixture through a fine-mesh sieve, pressing with a rubber spatula to release as much liquid as possible; discard solids. Add water if needed to yield 3 cups.
Divide among ten 2 1/2 ounce molds; insert wooden sticks, and freeze until solid, about 3 hours (and up to 1 week). To remove, dip bottom of molds in warm water for 2 to 3 seconds.