Answer:
Only two backbones and thousands of ribs.
Salty water everywhere but not sea in sight.
A beggar's brother went out to sea and drowned. But the man who drowned had no brother. Who was the beggar to the man who drowned?
What I am filled, I can point the way. When I am empty. Nothing moves me. I have two skins. One without and one within.
My first is high, My second damp, My whole a tie, A writer's cramp
You use it between your head and your toes, the more it works the thinner it grows.
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?