Found this song in my head the other day, and went back to listen to the song again. Found this comment on the video explaining the title of the song and its origins:

"This is called Confluence. It is a tune native to the Minneapolis/Saint Paul shanty sing scene, written by the person singing it in this video, Michael Shewmaker."

Shewmaker is a published poet, but his book, Penumbra, doesn't appear to have a song by this name in it.