Mix graham cracker crumbs, melted butter, and 1/4 cup white sugar in a bowl. Measure 1/4 cup crust mixture and set aside. Press remaining crust mixture into a 10x6x2-inch pan.
Combine water, 1/2 cup white sugar, and gelatin in a saucepan over medium-low heat; cook and stir until gelatin and sugar dissolve, about 5 minutes.
Stir sour cream and yogurt together in a bowl. Gradually stir gelatin mixture into sour cream mixture; stir in vanilla extract. Refrigerate until partially set, about 30 minutes.
Beat heavy cream in a glass or metal bowl until soft peaks form. Fold sour cream mixture into whipped cream; stir in blueberries. Spread blueberry cream evenly over crust; sprinkle reserved 1/4 graham cracker mixture over dessert. Chill in refrigerator, 8 hours to overnight.
