In "The Rime of the Ancinet Mariner," does the Mariner really love water snakes after just seeing them?
You are referring to Part IV in which the Mariner awakes to begin recognizing and appreciating nature and all creatures. He killed the albatross for no reason; he didn't appreciate nature nor recognize the fact that all living creatures deserve life and for this he was cursed. His curse - the unmoving ship and the lifeless crewmembers who each cursed the Mariner with his eyes as he died - is lifted only when he finally comes to this new realization. It's not that he loves water snakes so much as that he appreciates them for their beauty and for the fact that they are part of the universe of living creatures. To him, they are wonderful, beautiful creatures and in his new awareness, he is thrilled at being able to see the beauty.
The mariner's penence or punishment was to be on the ship with the 200 corpses. He fell in love with life rather than the water snakes. This is why he was gifted life from life in death. Because he was surrounded by death and he still managed to enjoy and love life