If you mean SWANEE RIVER...that predates Gershwin by life times and was written by Stephen Foster, who was America’s real first song writer and lyricist.
Different song.
Foster’s “Swanee River” is “Way down upon the Swanee River...”
Gershwin’s song is “Swanee”: “Swanee. How I love ya, how I love ya...” One of his first successful songs. Lyric s by Irving Caesar. Made famous by Al Jolson.
Gershwin and Caesar were complaining about some of the popular music, and Gershwin allegedly said, “Irving, you and I could write a better song in 15 minutes.” So they did.