Hydroid, Corymorpha microrhiza (formerly Monocaulus parvula), with highly cryptic nudibranch, perhaps Cuthona elioti. Could kick myself. Just to document this hydroid, I quickly fired off a shot, not realizing that there was a nudibranch on it!
Grytviken Pier, night dive
South Georgia Island
Thanks to Peter Brueggeman for the initial hydroid ID and this note: The round beads in this photo are probably the gonophores (sex cells) of the hydroid which arise between the oral and aboral tentacles.
Update from Paul Dayton (August 23, 2019): This hydroid is no longer paruvula but now is Corymorpha microrhiza.