Answer:
I am seen in the water. If seen in the sky, I am in the rainbow, a jay's feather, and lapis lazuli.
In we go, out we go. All around and in a row. Always, always steady flow. When we'll stop, you'll never known. In we go, out we go.
If you drop me I'm sure to crack. But give me a smile and I'll always smile back.
Flat as a leaf, round as a ring. Has two eyes, can't see a thing.
I march before armies, a thousand salute me. My fall can bring victory, but no one would shoot me. The wind is my lover, one-legged am I. Name me and see me at home in the sky.
What is so fragile that saying its name breaks it?
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?