Here's why:
* Imagery is the use of vivid and descriptive language to create a mental picture for the reader.
* The line uses words like "silvery," "splashing," "loitering," and "drink" to paint a picture of a serene river with horses taking a refreshing break.
While the line also has elements of personification (giving human-like qualities to the horses by saying they "loiter" and "stop"), the overall effect is to create a strong visual image.