Hi rling.  I have heard back from the Australian Museum’s, Janet Waterhouse who said: “Rling’s identification of Pseudobiceros bedfordi is correct and it is a flatworm. The other specimens filmed before and after the shot are all nudibranchs.  Bill Rudman had a comment on a similar photo he received on  sea slug forum: “This is a flatworm, not a nudibranch. Its name is Pseudobiceros bedfordi. It is sometimes hard to tell nudibranch and flatworms apart without having a close look. One good field indication though is how quickly they crawl. Your description of it as a fast moving slug is a pretty good indication that it is a flatworm. Nudibranchs are very slow”.  The film clip also shows the flatworm motoring quickly around cf the nudibranchs. It seems like it’s a pretty common mistake.”

Hi rling,  Being a 'fishy person', I would be way out of my depth if I tried to talk about nudibranchs.  I've forwarded your comment to the staff in our Malacology Section who will reply soon.

I was thinking of the animal they describe as a "nudibranch" which is actually a flatworm (Pseudobiceros bedfordi)! This is a pet hate of at least one well-known Australian naturalist...

Good call!  Like all the BBC footage, Episode 8 is great.  I just watched it here. I'm not a malacologist so don't take my word for it, but I suspect that the error you are referring to is the Humbolt squid's reputation as a man eater.  I found this page which refutes the claim.

Be sure to check out episode 8 "Creatures of the Deep" too -- it features Australian giant cuttles! I had a sneak preview on a recent flight. See if you can spot the mistake! (Hint: you may need to know a teeny bit about Opisthobranchs!)

I'm with you Kieren.  It was fantastic.  Several more of the clips from that fantastic show will be slowly trickled onto the site over the coming weeks.

Saw this and loved it! What stunning footage.