For Members: The rubber duck was available as a hidden item in the Penguin Style catalog, now it is not there. You'll have to wait for it to come back.
For Non-Members: It was available as a free item in the Summer Parties earlier, which haven't taken place since I joined club penguin (July 2010).
Chat with our AI personalities
you can't
You cannot get it. You can get the hula skirt though.
To get the duck in the water on mission 9,put the transmitter with it.Then,go to the iceberg and put it in the water.
You buy the rubber duck, (which is sometimes available in the catalog, or you can unlock it through a code.) Then you go to the cove where nothing else but the duck is there. Go in the water area and swim.
Not on the current Club Penguin but I think that they have old Club Penguin on Penguin Chat.