Answer:
Long and slinky like a trout, never sings till it's guts come out.
Always old, sometimes new. Never sad, sometimes blue. Never empty, sometimes full. Never pushes, always pulls.
Round like a dishpan and smaller than a bathtub. But the ocean can't fill it. What is it?
What is made of wood but can't be sawed?
I can move even when you are still. I can be one or many.
Break me and I am better immediately set and harder to be broken again.