There's a sadness behind it. The guy is also dealing with the death of a cinematographer (Dieter Plage) he took up last time. Yet again, Herzog managers to find a local, and explore his life, to make the film even more interesting. That's not to say the engineer lacked interest, but because he had to take time out to work on the craft, and for his own emotional being: coming to terms with the death that his work had caused before.
It's a great depiction of a man that needs to conquer his remorse, the canopies of the waterfall and himself -- to learn that his carelessness, his selfishness are what caused the accident, but never are we left hating the guy -- for his innocence and obsessive passion for the science leave us inspired just like the men that are driven by their inner being to explore the unknown before him.
The music and cinematography that are composed in this film are completely majestic. I was left in serene awe; some of the scenery you could admire in a trance for hours. One of his best documentary films without a doubt.