Here's why:
* Personification: Giving human qualities or characteristics to inanimate objects or abstract ideas.
In this sentence, the waves are described as "fading," which is an action typically associated with living things. The waves, being a natural phenomenon, don't actually "fade" in the literal sense. The author is using the word "faded" to create a vivid image of the waves disappearing into the mist, as if they are growing weaker and disappearing.