What am I?

Here's a poem I wrote because I realized my subject is almost everywhere.  Can you guess what it is before the end?

What am I?

I am liquid.

I am solid.

I am gas.

I am life.

I am the majestic falls and the bubbling creek.

I am humans, plants, animals.

I am the flowing force that drives the current.

I am the companion of thunder and lightning.

I am the underground river.

I am the clouds hanging in the sky.

I am the calm, clear pool in the woods.

I am the hurricane swirling and twirling.

I am blue and green and gray.

I am a mirror and a cyclone.

I am not air, or fire, or earth.

What am I?

I am water.