It's difficult to decide which version of this I like best. Posted one by Allan Hall here.
Here is Alison Krauss's version from a concert of the music from O Brother, Where Art Thou?. (Embedding disabled on the video.) Alison's voice is perfect. It's just...there.
There's something about this song that gets to me. It reminds me of the Flannery O'Connor story "The River." A disturbing and powerful story about a little boy who gets baptized.
Looks like a great concert (though I haven't had time to watch it) is available here on Youtube with all the music from O Brother. (Strange-looking movie, but wonderful music.) (Link HT: Southern Gospel Yankee)