Ask MidCurrent: How Do You Control the Speed of the Fly When Swinging?

Swinging flies involves using the pressure of the current against the fly line to make the fly move across the flow. Photo: Charles Hildick-Smith

Question: I’ve been working on swinging flies for trout, but I’m struggling with how you control the speed of the swing. What’s the secret?
—Jeff F., Rexford, NY

Answer: Newcomers to fly fishing with streamers and wet flies often simply cast across the current and let the fly swing downstream under tension, hoping a fish will strike. However, by adjusting a few key factors – namely the speed of the swing and the depth of your fly – you can dramatically increase your chances of hooking fish.

As in “to Swing”

“Fishing on the swing” refers to a classic presentation where you cast your fly across or down-and-across the current and let it drift under tension in an arc across the flow. As the line comes tight, the fly swings in a broadside presentation, imitating a swimming baitfish or emerging insect. Unlike a dead drift, where the fly moves naturally with the current, a swung fly is in constant motion, a key trigger for predatory fish. The angler typically casts across the stream, then lets the fly swing until it is directly downstream, covering water in the process. Swinging flies is particularly popular for steelhead, salmon, and big trout, but it can work in many situations. It is an efficient way to cover water when fish are active.

Swing speed and depth are the factors that largely determine where your fly is in the water column and how enticing its movement is. A fly swinging too fast near the surface might not tempt fish holding deep, especially in cold water. Conversely, a fly that’s swinging very slowly and deep could be exactly what sluggish fish want; or a faster, shallower swing might provoke a reaction strike. By understanding how to control speed and depth, you can adapt your presentation to conditions and the mood of the fish. Small adjustments in swing speed or depth can be the difference between a slow day and a banner day on the water.

How Swing Speed and Depth Affect Your Success

Speed and depth are closely linked in swinging presentations. Generally, a fast-swung fly will ride higher and shallower in the water, whereas a slower swing allows the fly to sink deeper into the fish’s zone. Fish behavior and water conditions dictate what combination is ideal. For example, in cold water, fish are lethargic and often hold near the bottom; they usually won’t chase a rapidly moving fly toward the surface. In those conditions, a slower, deeper swing is usually far more effective for enticing a strike. In warmer water or when fish are aggressive, speeding up the swing or presenting the fly higher in the water column can grab attention – some steelhead or trout will chase a quicker, shallower fly if they’re in a chasing mood.

Another factor is consistency of swing. Experienced swing anglers often strive for an even, steady swing speed through the drift, believing it maximizes the chances of a take. If your fly accelerates or stalls abruptly, it may put off fish. Achieving that consistent swing often means making adjustments early in the swing (when the line is in faster mid-river currents) and then letting the fly speed up slightly in softer water at the end, so that the overall movement appears uniform. Depth plays into this as well because ideally you want your fly to “hover” at the depth of the fish, not racing over their heads or dragging in the rocks. The ultimate goal is a controlled swing where the fly moves naturally, at the right speed and depth for the situation.

Five Key Ways to Control Swing Speed

While the river’s current provides the power for the swing, the angler has several tools to speed it up or slow it down. Here are five essential techniques to adjust swing speed, and you can use them individually or in combination:

1. Mend Your Line. Mending is the most common way to adjust swing speed. In simple terms, an upstream mend will momentarily reduce tension and slow the swing down, while a downstream mend will increase tension and speed the swing up. A big upstream mend allows the fly sink before coming under tension, whereas a downstream mend drives the line into a quicker arc. Make your mend early in the drift, right after the cast, for maximum effect on swing speed.

MidCurrent Editor-in-Chief Phil Monahan caught this gorgeous char by swinging a Dolly Llama streamer across a submerged ledge at Tikchik Narrows, Alaska. Photo: Charles Hildick-Smith

2. Change Your Casting Angle. The direction you cast relative to the current greatly affects swing speed. Casting straight across (90 degrees to the current) means more of your line gets caught in fast water, so the fly will swing faster. Casting more downstream at a shallow angle results in a slower swing, because less line is pulling in the fastest current. In practical terms, if you want a slower, deeper presentation, cast more down-and-across; for a faster swing cast more directly across. Don’t worry about casting to the far bank every time; instead, cast to where you can control the swing effectively.

3. Move Your Feet. Your physical position in the river changes the swing. If you wade a few steps farther out into the river, you shorten the line distance between you and the fly, which in turn slows the swing because the current has less line to pull on. If you are closer to the bank, you lengthen the line in the current and the fly will swing a bit faster. Simply moving a step or two can alter the fly’s speed enough to interest a fish, so adjust your stance in addition to mending.

4. Reposition Your Rod Tip. Think of your rod tip as the anchor point of the swing. By changing rod-tip position, you effectively change the length of line exposed to the current. Reaching your rod tip out high and toward the center of the river (especially with a long rod) can slow the swing by reducing drag. In contrast, pointing your rod tip low and toward the downstream bank will put more line in the faster current, creating a downstream belly and speeding up the swing. Also, if mixed currents threaten to accelerate or stall your fly, you can repeatedly lift or dip the rod to keep the line moving evenly. Good rod tip control can “fine-tune” your swing speed on the fly.

5. Lead or Follow the Fly. This is a subtler rod tip technique. Rather than always pointing the rod directly at the fly, try following slightly behind the fly’s path as it swings. Keeping the rod tip trailing behind the fly (i.e. pointed a bit upstream of the fly’s position) puts a touch of slack in the system and slows the swing slightly, often presenting the fly “butt-first” to the fish. On the other hand, leading the fly (rod tip slightly ahead of the fly’s motion) will tighten the line and form a belly, speeding up the swing and presenting the fly more broadside to the fish. Each approach can have its moment. A slower, butt-first swing can look like a baitfish casually wiggling, while a faster broadside swing might imitate prey trying to flee. Experiment with rod positioning as your fly swings and watch how it affects the fly’s pace.

Using these methods, you have a lot of control over how fast your fly swings. For example, if you need to slow down in a swift run, you might cast slightly downstream, throw an upstream mend, wade a step deeper, and hold your rod high to minimize drag—your fly will crawl across at a snail’s pace. Conversely, to speed up the swing, you could cast square across, do a slight downstream mend, and even lead the fly with your rod tip to hurry that fly along. By actively managing swing speed, you’ll be able to tailor the presentation to what the fish want on any given day.

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