As those of you keeping up with the story know, the oceans on the world of Elancia are dying one by one, the waters become glassy and warm, and monsters roam them constantly. Eventually, the water turns to sand. For the many ports of this world, this sea-death has been a death-sentence. Many sailors have turned to lives of crime, too.
The first time this song is heard is in Granport, which is in Celestion, right at the beginning of Season 1!