Quote: It seems like the hydraulics would be dangerous...as well as the underwater obstacles being dangerous to limbs, spine, etc?
As far as I understood back then, the hydroelectrical dam will ruin the rapids below it (northwards), as the amount of water in the river will then vary a lot more then it does naturally.
Back to the snakes, it was in the eddies where we entered and exited the water that they could sometimes be seen. And obviously not in the rapids themselves.