Tubeworms, or more specifically Featherduster worms, are annelid worms like the earthworm. While the two are only distantly related (earthworms being oligochaetes and tubeworms being polychaetes), one can definitely see the resemblance when the creature has exited the tube. They can crawl about by concraction and expansion, and do not need a tube of their own construct; rather, any 'bolthole' of suitable size is used. I had one that lived in clear airline tubing. Very neat to view.