Swimmers usually want to swim fast or swim more efficiently at some point. To swim fast means swimming a set distance in less time once in a while. Swimming more efficiently means swimming a workout or a race distance in the same amount of time but at a lower energy cost. To swim fast, either swim a distance faster or swim that distance with the same speed but using less energy... and then there is the "I want it all" swimmer. They want to swim fast and swim efficiently; that could happen, too, and will in the best case.