Short answer: wet flies are fished below the surface and swung across the current, and they're one of the easiest, most effective techniques a new angler can learn. If you're catching fish but feel like you're missing something, this is probably it.

I started using wet flies and it changed how I fly fish. I can recall fishing with friends early on and being relatively successful. Then Tom came to me, handed me a small box of wet flies, and gently whispered, "I'm going to show you one of my secrets." He took me into Bear Trap Canyon and showed me the art of swinging wet flies in seams. It was like a whole new world — an entirely new technique that was easy and effective.

What are wet flies?

Wet flies are a category of flies fished below the surface of the water. Unlike dry flies that float on the surface, wet flies imitate aquatic insects and other underwater prey. They can be highly effective, especially when fish are feeding below the surface — which is most of the time.

The aquatic insect life cycle

Before we get into technique, it's worth understanding what you're imitating. Trout primarily feed on aquatic insects, which include nymphs, emergers, and adults. These insects live beneath rocks, logs, and organic debris in the river. As they develop, they either crawl to the banks to hatch or generate gas bubbles to rise to the surface.

That rising phase is the key. A trout sees an emerging insect ascending through the water column as an easy, defenceless meal — and a swung wet fly imitates exactly that motion. It's why the technique works even when nothing is happening on the surface.

Traditional vs modern wet flies

Traditionally, wet flies were simple patterns made from natural materials like feathers and fur. They imitated various insects and were swung across the current. Modern wet flies have evolved, incorporating synthetic materials and more intricate designs, and some mimic baitfish or other underwater creatures.

What do wet flies imitate?

Caddis hatches: Caddisflies are prevalent in rivers and streams. Their larvae live underwater and are a favourite food source for trout, so wet flies resembling caddis larvae can be highly effective. More on that in how to fish a caddis fly.
Mayfly hatches: Mayflies are another essential insect for trout. Their nymphs, emergers, and duns provide consistent meals, and matching size and colour matters.

This article will help you formulate a way to select flies.

Techniques for fishing wet flies

Swinging wet flies: Cast down and across the current, then let the fly swing naturally as it moves across the water. The current does the work. As the line comes tight, the fly rises through the water column — imitating an emerging insect and drawing strikes from fish holding in the seam. This is the technique Tom showed me, and it remains one of the simplest ways to cover water effectively.
Wet flies under a strike indicator: Similar to nymphing, use an indicator to suspend your wet fly at a specific depth. Adjust based on where you believe fish are feeding.
Leisenring Lift: After your wet fly swings across the current, perform a subtle lift with your rod tip. This mimics an emerging insect rising toward the surface, and it often triggers a strike at exactly the moment the fly changes direction.
Selecting the right fly line: A weight-forward floating line works well for wet fly fishing, letting you cast accurately and control the swing. The Moonlit Performance WF Taper Floating Fly Line is a solid choice. If you're swinging in deeper or faster water, a Floating Intermediate Sink Tip S1 gets the fly down while keeping the running line manageable.

Choosing the best wet flies

There are countless patterns, but a few traditional favourites do most of the work:

Soft hackles: Simple yet effective, soft hackle wet flies imitate emerging insects. Their soft, mobile fibres pulse in the current and create a lifelike appearance that stiffer materials can't.
Woolly Buggers: Versatile flies that imitate leeches, baitfish, and other underwater creatures. Their movement attracts aggressive strikes. The Crystal Woolly Bugger Assortment covers five patterns.
Pheasant Tail Nymphs: These resemble mayfly nymphs and work in a wide range of water conditions. The Bead Head Pheasant Tail Assortment gives you three sizes.

If you're starting from nothing, the Basics Collection Bead Head Nymph Assortment gives you ten wet flies across five patterns, and the Postfly First Cast Beginner Trout Assortment is thirty flies covering surface and subsurface. For bigger water and aggressive fish, the Fly Rod Chronicles Freshwater Streamer Assortment. Browse all fly patterns and assortments.

Tying your own soft hackles? The fly tying collection has hooks, thread, and hackle — and soft hackles are genuinely one of the easiest patterns to learn to tie, which makes them a good first project.

Remember, experimentation is key. Observe the water, pay attention to insect activity, and adjust your selection accordingly.

Leader setup

For wet fly fishing, use a longer leader — typically 9 to 12 feet — to allow the fly to swing naturally. Tapered leaders with a tippet of 4X to 6X are suitable, and you should adjust leader length based on water depth and the presentation you want. Below 4X isn't advised for swinging, though it's fine under an indicator, because a swing puts direct sideways pressure on the tippet the moment a fish takes.

Stock up on Stone Creek Mono Tippet and see all leaders and backing.

This video shows my preferred method, or formula, for a swinging wet fly leader.

The bottom line

Wet flies offer a dynamic approach to fly fishing. Whether you're targeting trout, bass, or other species, mastering the swing can lead to exciting and rewarding days on the water — and it's a technique that catches fish when nothing is showing on the surface, which is most days.

If you take one thing from this: go find a seam, cast down and across, and let the current do the work. That's the whole secret Tom handed me in a small box.