Grease your 1 large or 2 small bundt pans. Sprinkle the chopped pecans over the bottom and set aside.
Combine the cake mix, pudding mix, ½ cup rum, water, oil and eggs. Beat for 2 minutes on medium speed. Pour into prepared pans. Bake at 325 degrees for approximately 45 to 50 minutes, or until done.
While the cake is baking, prepare the hot rum glaze. Combine the sugar, butter, rum and water in a small saucepan. Boil gently for 2 minutes. Remove from heat.
When cake is done and still in the cake pans, prick the warm cake with a toothpick many times to make small holes. Pour the prepared hot rum glaze over the hot cake. Allow to cool in the pan for about 15 to 20 minutes. Turn out onto cake platter and decorate.