Never figured out exactly what these guy were. As the summer went on the creek turned into a series of pools and these guys were quite populous in the largest,deepest pond. They were pretty good at ducking out of view as you got close, even when I made sure my shadow wasn't tipping them off... They were fairly large - 3-4+ inches in length. Orange and white-ish colored - the exoskeletons were always floating around the edge of the pond but I still wonder what the adults looked like.