I don’t know how many words you really need for this one. This is a shot of a brown trout holding in a run. Those white blobs are all air bubbles.
I’ve done quite a bit of scuba diving in rivers with trout, as many of you know, and this image pretty fairly reflects what it looks like down there. When you look toward the river surface, you’re really looking at a mottled sheet of gray. The air bubbles are almost always present, and they almost always look white. Granted, what a human eye perceives and what a trout eye sees may well be different, but we do know that trout are able to differentiate colors.
Another thing I noticed with the mask on, was how trout react to things splashing on the surface. The splat of a plastic or cork bobber smacking down clearly spooks them much more than the sound of yarn or wool landing on the water does. It’s actually a fairly dramatic difference in calmer and clearer currents.
While I hope to spend more time sight fishing, and less time blind nymphing, this summer, there are times when sight nymphing with an indicator is extremely effective and very rewarding. But you need the right indicator–one you can see, but blends into the trout’s environment.
I choose white wool. It should be about the size of a marble (or an air bubble). And, it won’t make a distinct sound when it hits the water.