Worm (NB; is Not E.laticeps) Edithburgh SA
This is a VERY big marine worm,capable of very painful venomous bite,and more often seen by divers at night when foraging actively but on this day it was quite heavily overcast,rather late afternoon,and worm was in some sort of struggle/distress/??being attacked from below substrate by octopus??(guesswork….I cld not see even one occy’s arm,but I’m also sure the brittle star present is an incidental critter wrt ‘episode’ for worm)
PS:worm’s length can be roughly assesses based on the paddleweed(Halophila sp. seagrass) also present….Hmmm…
I’ve reviewed my comment and now think it’s more likely that the worm is in attack mode and not in a struggle to survive against a hidden predator,because these worms are known to often detach their tails (up to about a third of worm’s total length according to the books and I’ve seen an equally long worm drop about a quarter of its tail on a night dive decades ago at Port Stanvac just to south of Adelaide when it was attacked by various reef fish having been highlighted by our dive torches)…
…(continued)…and the worm in this Edithburgh image appears intact and I would easily have seen any dropped rear segments as the visibility was excellent with little tidal current ,also there were no interested predatory fish species anywhere near the very active worm.So I have decided that the worm had the situation under control,just wish I knew what it was attacking under the substrate or perhaps in a prey species ‘ den or silty small crevice.My best guess would be one of the many mostly quite small Keeled Octopuses (O.berrima) which are common under this jetty,or maybe one of the bigger octopus species also common there e.g. Maori Octopus.Perhaps the worm was biding time keeping a firm grip on an octopus while waiting for its venom to take effect.
Nothing to add!
Source: via David Muirhead on Oceandiscover