Cut the chilled jello into cubes and place in a bowl and set into fridge until ready to use.
In a small bowl, add the cold water and sprinkle unflavoured gelatin on top of the water.
In a medium-sied saucepan bring the pineapple juice to a boil
Remove pan from heat.
Add the gelatin mixture to the pineapple juice and stir until dissolved.
Pour the pineapple juice into a large mixing bowl and place in the freezer for about 20 minutes to cool.
Remove from freezer.(check to see that it is cooled)
Add the cool whip to the pineapple juice mixture, folding in gently. Do not stir too hard as you need to keep the fluffiness of the cool whip.
Add the pineapple/gelatin mixture to the cubed jello and fold gently until mixed.
Pour the mixture over the crust and smooth the top with a spatula or spoon.
Sprinkle the remaining 3 tbsp of graham crumbs over the top of the cake.
Chill for at least 3 hours before serving.