All of our flies are tied with UV reflecting materials, some reflect more than others. For example, iridescent feathers absorb most of the ambient UV, thus peacock herl is dark in the UV. OTOH, natural white duck quills and teal flank feathers reflect most of the UV. Thus you have the Coachman, Zug Bug, Prince Nymph, etc..
A killer dry fly for many trout fishermen is the Adams. Natural grizzly hackle is really interesting in the UV.
Adams in visible light
Adams in ultraviolet light
Regarding how far UV penetrates water, the max depth recorded is 600 meters. You can see videos of SCUBA divers at greater than 200 feet in fairly turbid fresh water with their fluorescent patches and swim fins glowing.
Another fly that we use is the Royal Coachman in all its manifestations. If the hairwing Royal Coachman is tied with natural white bucktail or kip, the result looks like this in the UV -
So, we are always using UV materials. We just might want to use them in ways to emulate the natural insect in the UV.
---------- Post added at 07:50 PM ---------- Previous post was at 07:34 PM ----------
Regarding that Eccles blog post, the distinction we need to make is that while mature trout may or may not retain some 15% UV specific cones
in the dorsal temporal retina, it doesn't matter to us fishermen. Because the L, M, S (RGB) cones all support a secondary peak in the UV. Further, the rods of the retina used at dusk and nighttime are very sensitive to UV and the percentage of solar UV increases at dusk. So, we will let the scientists battle out the UV specific cone issue, they all agree that mature trout have UV input from the RGB cones.
BTW, whitetail deer have a huge percentage of rods in their retinas, all the better to see at dusk and dark when they do much of their feeding. And, yes, they are sensitive to UV. Which is handy, because that white tail warning flag is highly UV reflective, allowing the herd to follow the leader at top speed when fleeing from a predator in near dark conditions.