The modified wet fly swing is adjusted to fish weighted flies or sink-tip lines along the stream's bottom. The modification is that the cast is directed three-quarters upstream instead of slightly downstream; this change permits the fly and line to sink deeper. Otherwise, this technique is identical to the wet fly swing with perhaps the additional need for some line mends. Swinging deeply through its arc, the fly is presented along the stream's bottom.
Mends are made as necessary in the appropriate direction. These mends help sink the fly deeper because mending prevents line drag from pulling upwards on the fly.
When the fly is directly across the stream it has sunk to its deepest position.
Additionally, line may be played out to maintain the fly's depth and to retard the swing of the fly.
Retrieve sufficient line so the cast can be remade. Stepping down a given distance presents the fly to a different area.
The step-down distance is adjusted to exact stream conditions such as: feeding lane size, water clarity, temperature and light intensity. For example, when conditions favor inactive fish, the step-down distance is made shorter (perhaps only a foot or two); conversely, when conditions favor active fish the step-down distance is made longer (perhaps three to eight feet). In this way efficient presentations are made to thoroughly fish large riffles or holds.
"Modified Wet Fly Swing." Fly Fishing: The Lifetime Sport. . Encyclopedia.com. 24 Apr. 2019 <https://www.encyclopedia.com>.