I've caught quite a few swinging over the years on one particular Chehalis river trib. Conditions were always the same, fishing a day or two after a high water event. Dropping water with the fish traveling and fishing the softer inside seams of choppy, riffly water. The main river would be chocolate colored at times, but the softer inside water offered much better clarity. Long casts weren't necessary, just enough to get the head out in the current past the seam. Sometimes the fish are incredibly close to shore. At times so close you really can't swing for them. We showed up one day and a couple of guys fishing gear were blasting out to the middle of the river. My buddy did a roll cast to get the head out for his first cast of the day and a silver grabbed his fly 5' off shore. That turned out to be just an incredible day of fishing. We fished Teeny 200's cut back to 18'. Both weighted and unweighted black, cerise and purple bunny leeches with chartreuse heads did most of the damage. Something about a chartreuse head really turns the fish on, especially in colored water. As Flyborg said, it is very very difficult to get them on the swing when they are stacked up in the deeper holes.