This afternoon, while fishing at Lake Forest, one of several lakes managed by the Pagosa Lakes POA near Pagosa Springs, CO, i experienced a very interesting and unusual weather phenomenon. I was fishing from shore, about 100 feet from a small fishing pier, when I heard a sudden, loud roar. I spun around in reaction to it and saw water being lofted into the air and going in circles around the fishing pier. It was very loud and intense, like I was standing 100 feet from a waterspout. But this was no waterspout, because it was not pendant from a cloud - there was nothing in the way of clouds in the area except for a few small fair-weather cumulus. So I guess I would classify it as a water devil - like a dust devil, but over water and lofting water instead of dust. The votex moved farther out onto the lake (toward the east or northeast) irregularly and with what seemed like a subvortex or two. Then it was all over, within the time of maybe a minute. Wish I had been able to get some video but it all happened too fast. A couple that had been fishing on the pier had just left it and were walking up the road behind me when it happened. My guess is that if anyone had been on the pier, there is a good chance they would have lost some equipment into the lake, at a minimum. As it was, the inflow to it when it was 100 feet away blew the lid off a small stool I had next to me and tipped over the stool. Would have done a lot more to anything in the actual vortex. My guess, since the lake water is cold from mountain snow runoff and the day was hot, is that the vortex formed over land as something like a dust devil and moved onto the lake, but it clearly reached its peak intensity over the lake and I did not see or hear it until it was over the lake (but near shore). It was a warm day with the temperature around 86 or 87, and I would guess the low-level lapse rates were fairly steep, at least over land (but I would think less so over the cooler lake). I also noticed a few minutes before the water devil occurred that the wind, which had been southwesterly, shifted to northerly or northeasterly, so there may have been some kind of boundary or shear line that contributed to its formation. As soon as it formed, I experienced southwesterly inflow into it (it was to my north) and the wind stayed southwest for a while afterwards. Interesting and unusual - in a lot of storm chasing and a lot of fishing, I have never seen anything quite like this.