What is a living thing?

What I know:
A living thing is something that can breathe, like a plant, like human or an animal. It is something that can develop and grow like a tree, something that can die, something that can be born.

What I want to know:
I would like to know how can an animal survive in the water, how do they eat and how do they live in other places (not their habitat) and how can they adapt.