Preheat the oven to 350°F (175°C).
Combine the crushed pretzels, melted butter, and sugar in a bowl until evenly coated.
Press the mixture firmly into the bottom of a 9×13-inch baking dish.
Bake for 10 minutes, then let the crust cool completely.
Beat the softened cream cheese, sugar, and vanilla until smooth and creamy.
Fold in the whipped topping until fully combined.
Spread the cream cheese mixture evenly over the cooled crust, making sure to seal it all the way to the edges of the dish.
Dissolve the gelatin in the boiling water and allow it to cool until slightly thickened but not set.
Arrange the fresh blueberries evenly over the cream cheese layer.
Slowly pour the cooled gelatin over the blueberries.
Refrigerate for at least 4 hours, or until completely set.
Slice into squares and serve chilled.