Symbolism, Imagery, Allegory
One of Christianity’s symbols is the Jesus fish, or ichthys. (It looks like this.) Remember that when Addie dies, Vardaman associates her with his fish, which he has just killed and cleaned himself. When Vardaman focuses on his family eating the fish, we can’t help but think of Jesus and the Last Supper, when he has his disciples eat his own flesh and drink his blood. Here’s another case of ironic inversion: Addie might die like Christ, having sacrificed her life for others, but she is never resurrected. The closest we get to resurrection, in fact, is the image of her coffin heaving up out of the water. This is a horribly twisted version of the classic biblical story, just like much of As I Lay Dying is an inversion of the classic Quest (again, see "Genre" for more).