This movie is the first to qualify for the New Zealand Government's "Large Budget Grants Scheme" where the film-makers will receive up to 12.5% of their production budget back.
After the guys regain safety from the rapids, and unflip the canoe, they appear to be in calm water. Seconds later they are back in rapids again, and fall down a waterfall, there would be no way for the water to be calm right in front of a waterfall.