Add the water and juice to a small bowl and sprinkle the gelatin on top of it. Mix until combined and set aside for about 5 minutes for the gelatin to bloom. If it doesn't bloom, discard and repeat.
Chop 1 1/2 pounds of peaches, add them to a large bowl and sprinkle with 4 tablespoons of sugar. Set aside for about 5-10 minutes.
Add them to a food processor and pulse a few times until the mixture is smooth.
Add the heavy whipping cream, vanilla. lemon juice, and powdered sugar to a large bowl. Using a hand mixer whip the mixture until stiff peaks form.
Give the bowl with gelatin a stir and melt in the microwave for about 30 seconds or just until the gelatin dissolves. Do NOT bring to a boil.
Pour the gelatin mixture into the pureed peaches, stir well, and after that fold carefully into the whipped cream.
Chop the remaining pound of peach slices and sprinkle with 3-4 tablespoons of sugar. Mix and let stand for 10 minutes.
Stir again the peaches and place some into the bottom of each serving glass. Top with the mousse mixture.
Chill for about 4 hours in the refrigerator or until the mousse is set.
Garnish with the remaining chopped fresh peaches and more fresh homemade whipped cream.