Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.
The clumsy-looking mayfly nymphs of the genus Baetisca are surprisingly good swimmers.
Water boatmen are excellent swimmers, and you can see here how they use their oars to push themselves through the water, a motion easily imitated by the fly fisher.
Damselfly nymphs are among the most effective invertebrate predators in freshwater. You have to see one in motion to get a feel for their slow, deliberate style of stalking.