An Aquatic Riddle

By BlueWake

Sunlight above,
deep shadow below,
a twist and a turn
in the clear melted snow.

The clown of the river,
the fool of the stream,
a streak of dark brown,
perhaps just a dream.

I cut through the water,
I slice through the waves.
Nothing can stop me
as I swim past deep caves.

I come to the surface
and peek out at you,
a twitch of a whisker,
I'm back in the blue.

I snap at a fish,
am rewarded with dinner,
I laugh silent laughs
in the blue-greeney glimmer.

Can you guess what I am?
Undefeated in water,
do I still have you stumped?
But of course, I'm an otter.