Answer:
Who keeps the ocean clean?
I wiggle and cannot see; sometimes underground and sometimes on a tree. I really don't want to be on a hook and I become a person when combined with “book”.
I am the noise Santa's reindeers make
I rise and fall no matter what, only at finals rest do I not budge. What am I?
I can swim but never get wet. I can run but never get tired. I follow you everywhere but never say a word.
What is always coming but never arrives?