I've tried what I'd believed was the old taxonomic label Electroma georgiana but no go.
Growing rapidly on cork-weed Scaberia aghardii.

NOTE:
ALSO in image are a few Zyzzyzus spongicolus (Hydrozoa). These small polyps to 10mm height are "Found always on sponge, on jetty piles and shaded reef..."( Karen Gowlett-Holmes' A field guide to the marine invertebrates of South Australia 2008 p30).