Here's why:
* Personification is giving human qualities to inanimate objects or abstract concepts.
* In this sentence, the waves, which are an inanimate object, are described as "fading", which is a human action. This gives the waves a sense of agency and movement, even though they are simply water.
The sentence creates a vivid image of the waves gradually disappearing into the mist, which enhances the overall imagery and atmosphere of the scene.