Puree 4 cups of 1/2 inch cubes seedless watermelon, 1/2 cup splenda, and 2 tablespoons of lime juice in a blender. Pour into a 9x13 inch dish and place in freezer. Stir with a fork every 30 mins until mixture is slushy, up to 2.5 hrs. Spoon mixture into glass and enjoy! Add a shot of vodka to your drink if you like!