Preheat oven to 350 degrees F (175 degrees C).
In a medium bowl, combine graham cracker crumbs, melted butter and 1/2 cup sugar. Press into the bottom of an 8x12 inch baking pan.
In a large bowl, combine cream cheese, eggs and 1/2 cup sugar. Beat until smooth. Spread cream cheese mixture over crust.
Bake at 350 degrees F (175 degrees C) for about 15 minutes.
For the blueberry filling: In a large sauce pan, combine blueberries, water, corn starch and 1 cup sugar. Cook and stir until thick.
Spread blueberry filling over baked cream cheese mixture. Let cool. Top with whipped topping. Refrigerate overnight before cutting into squares and serving.