What “saves” the mariner? How does he react to the natural world?

It isn't until the mariner has his epiphany, courtesy of the slimy sea-snakes, that all living things are sacred does his re-birth take place, "thousand slimy things/Lived on; and so did I", meaning that he nor the dead men were better than God's other creations. The albatross slips off his neck and the Mariner then spends his time cornering people to make them hear his story.