Chop 2 cups of berries. In saucepan combine sugar and cornstarch. Slowly add water to combine smoothly. Add chopped strawberries. Cook, stirring constantly until mixture thickens and boils. Cool in refrigerator for about half hour. Pour about 0.75 of mixture into prepared pie crust. Stand up whole strawberries in syrup (to fill crust). Pour remaining syrup over strawberries. Chill until firm (about 3 hours). Spread cool whip over top of pie and serve.