(sorry for the low video quality - that's partially Blogger's doing)
They are kind of scud-like, but propel themselves differently. The have lateral filaments similar to some burrowing mayflies, but are not mayfly nymphs. This is why god gave us entomology professors. Professor Malcolm Butler from North Dakota State University had no problem identifying them as fairy shrimp.
It seems that they are so slow and meaty, trout often eat them up to the point of complete extermination. Therefore it's likely that if you see fairy shrimp, you won't see trout. That held true where I found them. And for some reason, they often occupy seasonal pools - indeed, I found them in a cutoff oxbow from a lake's outlet stream.
Trout apparently do coexist with them in some places like Montana's Blackfeet Reservation lakes, however, so do further investigate if you find fairy shrimp. If there are fish, they'll probably be fat.