In saucepan, over medium heat, combine the peaches, sugar, and water. Bring the liquid to a boil. Reduce the heat to medium low and simmer for 5 minutes. Remove from the heat. In a blender, puree the mixture until smooth. Add a enough water to thin the puree out into a peach juice.
Refrigerate until chilled. Fill each flute glass 2/3 of the way with Champagne. Add the peach juice and serve.