Image courtesy of the NOAA Office of Ocean Exploration and Research, Northeast U.S. Canyons Expedition 2013.
"Bramble" bamboo coral. These colonies (at least when "younger") have very thin branches and grow in these tangled thickets. You can see the polyps arising from several branches; they are very widely spaced along each branch. There appears to be a sponge intertwined with the bramble; the parts of the sponge that are brownish are dead, and the living parts white. Download larger version (jpg, 1.6 MB).