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.
One winter day, there was a man standing in the middle of someone's front yard. The person stayed there for several weeks without moving and the owner of the yard didn't mind. Eventually the man left. Who was the man?