Clean riddles

I look flat, but I am deep, Hidden realms I shelter. Lives I take, but food I offer. At times I am beautiful. I can be calm, angry and turbulent. I have no heart, but offer pleasure as well as death. No man can own me, yet I encompass what all men must have.

I can fly but I have no wings. I can cry but I have no eyes. Wherever I go, darkness follows me. What am I?

We can be boring, Or interesting. We can be long, Or short. We can have pictures, Or just words. Many love us, But many also hate us. What are we?

I had no father, only a grandfather. I shall bear no sons, only daughters. What am I?

I hiss. I can be poisonous. I am long. I have a forked tongue. What am I?

If you have me, you want to share me. If you share me, you haven't got me. What am I?

Where can you find rivers with no water, cities with no buildings and forests with no trees?

I have no life, but I can die, what am I?

There was a railroad crossing without any cars and trucks! Can you spell that without using any "R"?

In a supermarket, the first 25 customers of the day purchased an average of two items each. After a further 15 customers, the average number of items purchased by each customer rose to eight. What was the average number of items purchased by the last 15 customers only?