1. In large saucepan combine water, sugar, and gelatin. Bring to boiling, stirring to dissolve.
2. Place undrained peach slices in blender. Cover; blend until smooth. In extra-large bowl combine gelatin mixture, pureed peaches, peach nectar, and lemon juice. Divide peach mixture among four 1-quart containers. Cover and freeze overnight or until firm. NOTE: Mixture can be frozen up to 3 months. Use as many containers as needed to continue with Step 3. (Each quart makes 6 servings.)
3. To serve, place one or more containers at room temperature for 1 hour. Break in chunks with large fork. Place in punch bowl or jug. Stir in 2 bottles of ginger ale per container of peach mixture until slushy. Makes 24 servings (four 6-serving batches).