I noticed this crop circle looking thing on my back glass recently and I'm just curious as to what it is. I've attempted searching the internet, but everything I search comes back with tube worms. I have tube worms and know how they normally look this doesn't appear to be a tube worm. The only way I can describe it is a crop circle. It has a nice tight spiral with a wave like pattern. It's roughly the size of a quarter or a half dollar. I've never seen this before, but it actually looks kinda cool. Just curious if anyone know what this could be and its something I need to scrape off and siphon out. This image shows the squiggle pattern the best. Top middle on the glass. This show the circle pattern overall.