This photo is of a cluster of horseshoe worms, Phoronopsis albomaculata Gilchrist, 1907 in Paterson Inlet, Stewart Island. They are a member of the phylum Phoronida, which have a U-shaped gut that loops back so that the anus opens close to the mouth. The feeding tentacles entirely surround the mouth in a horse-shoe shape arrangement called a lophophore.
Image credit: Karen Gowlett-Holmes, Figure in Gordon, 2009, p 268.