To be dead in the water means to be completely defunct, but in this sentence the person is wondering how things would have gone if they had found the other person functioning properly.
Consider the staetement "Watching her now, I wondered how things would have gone for me if I had found her very much alive and functioning properly instead.". Based on this statement, is "Watching her now, I wondered how things would have gone for me if I had found her dead in the water instead." a true statement? Yes/no/unknown