Best riddles for teens

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

Thirty white horses on a red hill. First they champ, Then they stamp, Then they stand still. Who are they?

I can be as thin as a picture frame but my insides have many things you can see. What am I?

What do you get if you add 3 to 300 five times?

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?

Someone said you sounded like an owl.

I sleep when you are awake, I am awake when you fall asleep. I can fly but no feathers to aid my flight. What am I?

Where does Valentine’s Day come after Easter?

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