Looks like a lace wing. I do not think they are an aquatic insect. However, I could easily see them ending up on the river. They are pretty common this time of year, and will be around until the first hard freeze.
I have never seen one on the river, but that means nothing as my river days are usually over by the end of September.
Thanks for the reply. I was trying to research/refer back to this topic and to clarify my original post. I think this is the bug I was finding on the river. So; it may not be stone-fly as I originally thought two-years ago when I did not have a camera. I tried using all the online identification tools to figure it out; but, I am still stumped. I see them in yellow and in green on the river. Also; I have been finding a few October Caddis Adults in the evenings while walking along the river.
Another odd find for me has been some blood-type worms/midges on the lower end. I seined one two-weeks ago but, did not have any containers to save it in.