Hard to tell by the picture. Are they non calcareous tubes (sand and mucous) or calcareous tubes (hard)? Do you see anything come out of the ends; like feather dusters or two tentacles?
Yeah those are bad pics, sorry. I'm trying to get another. But they look more calcareous and it looks almost like two eye's at the bottom with little tenticles coming out from it which seem more like small feather dusters to me. They seem to be popping all over and in this shot which I know is still pretty blurry (sorry) there is a depression in the gravel that it seems to have made.
You can (hopefully) kind of make out the two eye looking things in this shot: