A good example was this last spring up on the Sauk. Low and clear till the last week. You see, steelhead didn't grow to maturity by being stupid, they know when conditions are such where they feel secure. Low lighting such as found at daylight and dusk find steelhead holding and moving through soft and or shallow waters. They know predators can't see them.
Dirty water does the same thing.
Because that's when the really big boys feel comfortable about lying in close. Because at first light, the unmolested steelhead are lying in soft shallows and these fish can't see the leaders. As conditions change to bright and sunny, the water clears and angling pressure increases, steelhead naturally move into waters that are deeper and faster. Line shadow and boat shadow both produce hide and seek conditions. They feel exposed.