"Cool Water" is a song written in 1936 by Bob Nolan. It is about a man and his mule, Dan, and a mirage in the desert. Members of the Western Writers of America chose it as one of the Top 100 Western songs of all time.
Hank Williams recorded the song in 1948 or 1949 for the Johnny Fair Syrup Company radio show on KWKH in Shreveport, Louisiana. The recording is available on The Complete Hank Williams boxed set, released on Mercury Records in 1998. It also appears in the film Rango, set in an Old West town populated by animals that is suffering from drought. Every Wednesday, the townspeople perform a ritual they believe will return water to their town, during which the song plays over a PA system.