Cold fingers, cold fly line running through, past your index and middle finger.
Shivering legs, the long underwear and flannel and jeans aren't enough.
Cold, rosy cheeks, the wind funneling past.
The cold seeps through.
Then the wool indicator dips, the tiny nymph's been taken.
Or, then, the line tugs, resists - there's a bump, a pull, a hit on the meaty streamer. The set's instinctual. The rod comes to life, shaking with the excitement of the fish and current.
You strip in line, the cold's irrelevant now, but it still burns your fingers as the line runs through. Minutes later, fish in the net, you dip your hands in the stream. Damn it's cold, ice cold, cold as cold could be. Your hands are red when you hold the fish, get the hook out of him.
Then, maybe, a little photographic evidence. Proof of skill, of endurance, or luck largely. Bragging rights back at the cabin around a fire with good buddies and some bourbon. Embellishment will be required.
Then he's back, back into the crystal clear, where he belongs.