In my younger days, one of my favorite fishing methods was to fish slower moving pools with nymphs. It takes a keen eye to detect strikes (which I don't have much of at my age) and patience.
I liked fishing an unweighted nymph, treated with some fly sink, in slow pools by casting quartering upstream and would treat the leader with floatant up to the point that the remaining untreated leader would allow the nymph to sink to the appropriate depth. You also need to use as light as tippet as possible to let the nymph act natural. I used a lot of 6X or 7X tippets.
My favorite pattern was a caddis larva or pupa, or a small Hare's ear type pattern in a color to match the time of the year... dark in early season, light brown/tan a little latter, and cream/white in the summer.
If you can "spot" the fish it helps, as you need to make your cast far enough ahead of the fish to get it to their depth, and general... right down their dinner plate. That usually requires fairly long, accurate, drag free casts.
Again, it takes some doing, but if you get it right, you can really take a lot of fish if you do, and can have some other fisherman really scratching their heads. LOL
The challenge of this type of fishing is what make fly fishing so much fun. The first time you catch a 16 or 18 inch hold over, or native brown trout this way... you won't forget it.
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