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.
A 400 yard long train, travelling at 30 mph, enters a 4.5 mile long tunnel.
How long will elapse between the moment the front of the train enters the tunnel and the moment the end of the train clears the tunnel?
A little pool with two layers of wall around it. One white and soft and the other dark and hard, amidst a light brown grassy lawn with an outline of a green grass. What am I?