syrphid fly larva

I found this little green larva in a mud puddle near Durango, CO, at an elevation of about 10,000 feet. It was really cold and there was a small amount of snow on the ground.

I couldn't tell if the little guy belonged in the water or had just fallen in... it wasn't exactly swimming or crawling on the bottom. So after taking these pictures I left it at the water's edge where it could go either way.