At an early point in the movie, McMurphy boasts that he is going to break out of the mental hospital by lifting a water fountain and chucking it through a window. The others don't believe him, so he bets them money he can do it. He ends up failing, but shames them all by saying, "But I tried, didn't I? Goddammit! At least I did that."

At this point, the water fountain becomes a symbol for McMurphy's undying sense of freedom. He never believes that anything is impossible. He will never stop trying to live life his way, and that's exactly why the folks at the hospital eventually give him a lobotomy.

Now someone else needs to pick up the torch of freedom from him, and that person is Chief Bromden. In a deeply symbolic moment, Bromden kills McMurphy and then lifts the same water fountain that McMurphy failed to lift earlier in the movie. Lifting the fountain is supposed to be impossible, but Chief reminds us that anything is possible for those who refuse to give in to authority.