Several years ago I was on the Green River in Utah below Flaming Gorge. We had hiked down Red Creek to the river and were returning up the canyon following the creek rather than on the trail. I was climbing up a narrow, rocky slot when I slipped and fell over backwards, landing on my back in the creek. When I started to sit up I found I had landed on quicksand. Each time I tried to get some purchase to get myself up my arm would sink into the sand. Finally was able to "swim" on my back to firmer ground and stand up. It was a scary couple of minutes.