For muddy, nasty water there's also THIS.
I've seen something similar in action — and actually drank the water, which was fantastic — when our friends in Canada used a flocculant they got at MEC on a canoe trip. Glad we had it because in Algonquin Provincial Park there are many piles of moose poop in the water that you can see while paddling the shallows.
If I were going to someplace like the Grand Canyon I would absolutely take this stuff and a collapsible bucket. Really amazing stuff for silty, turbid water.