You are walking along the beach, and all of a suddent a bright light comes falling from the sky. BAM!!! It crashes into the sand before you. It is a huge, silver ball glowing in the sunlight. You are afraid at first. Just then, the top of the ball opens. A little green alien pops up and says, "Greetings! I'm from Mars!" But then he sees the big waves crashing at the shore. Now he is afraid. He has never seen water before. You reassure him that it doesn't hurt, and that we need water. He wants to know why your planet needs water. You want to help him understand.