Make cake according to directions on box using the egg whites, oil and water; fold in 1/2 cup of coconut to batter. Pour into greased and floured 9x13 pan. Bake 23-25 minutes at 350 degrees until top springs back when touched and edges start to pull away from the edge of the pan.
While still hot, poke holes in top of cake with the handle of a wooden spoon. Pour 14oz. of the Cream of Coconut over top of cake. Cool to room temperature.
Stir the remaining Cream of Coconut into the Cool Whip and frost the cake. Sprinkle desired amount of additional coconut over the top. Cover and refrigerate, preferably overnight.