Outside, inside, inside, outside

i'm not 100% sure what this is about.

The tide moves slowly… in ..and out
The river flows with gentle trout
The air is still.. It blows so light
The moon is out on this night

The tide moves faster, out and in
The river rushes, the fish within
The air blows harsh on your chilled face
The moon is unseen through the clouds in this place

The tide moves crushingly, a tidal wave
The river's rapids you dare not brave
The air is screaming in your eyes
The moon's light flickers and dies

The tide moves slowly… in ..and out
The river flows with gentle trout
The air is still.. It blows so light
The moon is out on this night.