In a medium-size saucepan, combine sugar, vanilla, corn starch, lemon juice, and kosher salt. Whisk in water and mix until fully combined and no lumps exist.
Add in one half of the blueberries over medium-high heat. Bring to boil. Let the mixture cook until thickened, roughly 3-5 minutes.
Once thickened, remove from heat and allow the mixture to fully cool.
Fold in the remaining fresh blueberries and pour into the graham cracker crust. Refrigerate for 1-3 hours or until fully set.