The saltwater crocodile is a highly aggressive predator that opportunistically targets various types of prey for its food. It preys on mammals, birds, reptiles, fishes, and even humans. However, ducks, being primarily freshwater animals and highly domesticated, are unlikely to become prey for saltwater crocodiles. Ducks generally do not venture into the wild waters where saltwater crocodiles typically inhabit. Therefore, the occurrence of ducks swimming alongside wild saltwater crocodiles is unlikely. However, if such a situation were to occur, the crocodile would certainly attack and consume the duck.