When flying into the Sepik River area, the flight afforded some spectacular views of the river.  Notice how muddy the river is, this muddiness was noticeable when in a boat also.   It's also interesting to see the sinuous path of the river too.  As far as you could see, it wound all around the valley floor.

Notice the curved paths outside of the river.  These are called "oxbow lakes".  Rivers change paths over time and sometimes a the river will change it's path in such a way that a part of the river channel will be cut off from the river but still be filled with water.  Notice the curvy section in the bottom middle of the picture.  This is a very old oxbow which has filled in with dirt and trees have grown but it's still noticeable.