英语脑筋急转弯 | Flat, Yet Deep

Riddle:

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. What am I?

Answer:

An ocean.