The film's climax reveals that while Edward exaggerated the details, the essence of his stories was true. In the final scene at the hospital, Will finally stops fighting and tells his dying father the story of his escape to the river. This act of storytelling allows Edward to die in peace.
At the funeral, Will sees the real-life counterparts of his father's characters: the Giant is a very tall man, the twin singers are identical twins (not conjoined), and the ringmaster is a short, energetic man. They are ordinary people whom Edward turned into myths. This confirms that Edward didn't lie to hide a secret life, but to make the ordinary world magical. Will realizes his father was a 'Big Fish' who touched countless lives, and in the final shot, Will is seen telling these same stories to his own son, completing the cycle.