This video was filmed in the sewers below Cameron Village in Raleigh, NC, right down the street from me. The internet buzz was that it was some sort of viral campaign, but Deep Sea News contacted experts to find out what kind of creature this could be.

They are clumps of annelid worms, almost certainly tubificids (Naididae, probably genus Tubifex). Normally these occur in soil and sediment, especially at the bottom and edges of polluted streams. In the photo they have apparently entered a pipeline somehow, and in the absence of soil they are coiling around each other.