The father is in the hospital, dying, he asks his son to tell him how he dies. the son tells him this elaborate story about how he breaks him out of the hospital and drives him to a river, where everyone his father has ever talked about is there. the father turns into the BIG FISH and swims away. it then turns to the real funeral scene. The son realizes that his father wasn't lying, just stretches the truth to make the story more interesting. Son meets all the people that the father talked about. The last scene has the son his wife and mother watching the son's child play in the pool with his friends telling the stories told by the father. Another interpretation is that the stories told by Albert Finney were lies and the funeral scene was made up by the son as one final story to honour hes father, who he realised he did love for who he was.