The giant Salmonflies of the Western mountains are legendary for their proclivity to elicit consistent dry-fly action and ferocious strikes.
Dragonfly nymphs propel themselves through the water with a miniature jet engine, taking water in below their mouths and shooting it out their back ends. You can see the ripples from the jet out this one's back in this video.
This little Ephemera nymph swam around for a while and tried to burrow into the sand in my photography tank.