Answer:
Where humans breathe liquid.
What must be looked through in order to see?
I occur twice in eternity. And I'm always within sight.
What has a head, a tail, is brown, and has no legs?
I cannot be felt, seen or touched; Yet I can be found in everybody; My existence is always in debate; Yet there is a style of music named after me.
Two little holes in the side of a hill. Just as you come to the cherry-red mill.
Easy
Animal
Difficult
Food
Funny
Kids
Logic
What am I?