Call it what you will; I call it absolutely brilliant! Yay, nature! This was created by Hubert Duprat and some wickedly fascinating Caddisfly larvae just doing their thing. You can watch Duprat discussing his process here (about 2:30 in).
And here is a video of what the Caddisfly larvae build when they aren’t a part of Duprat’s “situation” (his word, not mine).