A red encrusting sponge? or a red blanket that has drifted down from the surface
? The field identification for this image was labeled sweater_sponge.
If a sponge, such sponges seem to be quite rare in the deep sea.
Image ID: expl6315, Voyage To Inner Space - Exploring the Seas With NOAA Collect Photo Date: 2011 July 14 Credit: NOAA Okeanos Explorer Program, Galapagos Rift Expedition 2011