easy
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.
Common Wrong Answers
“Lake”
While a lake is a body of water that can be deep and beautiful, it is usually smaller and more manageable than an ocean. It doesn't encompass all men must have in the same way oceans do.
“Desert”
A desert is flat and can be harsh, but it does not contain water and thus does not shelter hidden realms or offer food in the same way an ocean does.
“Sky”
The sky can appear beautiful and has depth, but it does not take lives in the same sense as the ocean does and does not provide food. It also lacks the physical attributes associated with a body of water.