Pour 2 cups of boiling water in a heat safe bowl. Add the grape gelatin. Whisk until gelatin is fully dissolved (about 2 minutes). Stir in 2 cups of rum. Divide the mixture equally in two bowls. To one, add 6 tablespoons of the coconut milk. Stir well. Add a little of the pearl dust to the transparent gelatin, if desired. Set both bowls aside.