In a 4 1/2 to 6 quart slow cooker, stir 2 3/4 cups water, rice, and cream of coconut and evaporated milk til mixed. Cover slow cooker with lid, and cook on low setting for 4 to 5 hours or on high setting 2 1/2 to 3 hours.
While pudding cooks, toast coconut; Heat small nonstick skillet on medium heat til hot. Add coconut; cook 4 to 5 minutes til lightly browned, stirring constantly. Transfer coconut to plate.
Remove crock fromslow cooker, Stir in rum if using. Let pudding stand 10 minutes. transfer pudding to nerving bowl. If not serving at once, press sheet of plastic wrap onto surface of pudding Refrigerate up to 2 days. to serve, spoon pudding into dessert bowls and sprinkle with toasted coconut. Serves 10