Short simple riddles for teens

What comes down and goes up again and again? What is that?

I eat other animals. I have a big mouth. I am green. I live in the water. Who am I?

What has a neck but no head?

When you have me, you feel like sharing me. But, if you do share me, you don't have me. What am i?

It can fill a room without occupying space. What is that?

What can go up a chimney down but not down a chimney up?

What can be swallowed, but can also swallow you?

There is something which arrested for attempting but not for completing. What is it?

If I drink something, then I am just over. However, I can eat anything. What Am I?

I live in a house called a coop. I have two legs, two wings and a tail. I eat worms and bugs and grain. I lay eggs. I am a...