Abe Sapien's origin in 'Shape of Water' contributes to the movie's theme of the 'other'. He is different from the normal humans in the story, being an amphibious creature. His origin being mysterious adds to the sense of the unknown, which is a big part of the movie's theme. It shows that there are things in the world that are not easily understood, and his character challenges the norms of the society depicted in the film.