Today’s tip falls within the ‘common mistakes we see a lot of’ category.
Most of us are well aware that any in-river structure (rocks, logs, snags, tundra clumps, ect.) make for potential holding lies for trout. Any object able to break up the speed of the current provides the opportunity for trout to hold comfortably in swift water and potentially provide cover from predators above.
Most anglers are also aware that not all fishy structure can be seen poking out of the water, but that submerged structures are often represented by a hydraulic feature on the surface itself. Boils, swirls, pockets, or any other funky texture on the surface of the water are generally an indication of structure below and are therefore worth targeting!
However, one mistake we see all the time when presenting flies to submerged structures is not casting far enough upstream of the target. Sure, we all know its important to present flies far enough upstream to imitate a natural drift, or to ensure the flies have ample time to sink (in the case of subsurface patterns), but when casting to a surface feature of a submerged object, its important to start your drift even further upstream!
Why? Because the hydraulic feature you’re seeing is always visible downstream of where the structure actually starts! Therefore, when fishing to a submerged structure, always start your drift well ahead of the surface feature (boil, swirls, etc.), because odds are the actual lie is further upstream than you might think.