You must choose one of those 1970’s Williams-scored Spielberg/Lucas flicks (JAWS, CLOSE ENCOUNTERS OF THE THIRD KIND, 1941, or STAR WARS). and write "The Song From..." that the film never had, in the style of a 1970’s pop tune (particularly in your instrumentation).
The song is written, both music and lyrics, and is called "Bad Fish". It has four verses, each one of which deals with a key scene in the movie, and a silly little chorus that's somewhat scathing about the protagonist of the story.
There was nearly an accidental reference to 'The Man in the Boat', which would have been quite apt, but it interrupted the flow of the song, so it was left out. There is another subtle reference, though, which I'll leave you to work out when you hear it.
The next step is to start the recording process and dig out suitable quantities of funky 70's pop sounds...