Quote Originally Posted by KarlB View Post
The beast is almost certainly a flat worm and not a Spanish Dancer. Don't know what species but will check some references when I get to work tomorrow.

Cheers
KarlB
After watching the video again I am even more convinced the beast is a Polyclad flatworm (Order Polycladida). According to the late Stephen Prudhoe (who was a world authority on these beautiful animals from the British Natural History Museum), it is generally not possible to identify the species "with any degree of certainty without a study of the copulatory complexes in serial section" (see Prudhoe, S. 1982. Polyclad flatworms (Phylum Platyhelminthes). In S. A. Shepherd & I. M. Thomas (Eds), Marine Invertebrates of Southern Australia Part 1(pp. 220-227). Adelaide: Handbooks Committee of the South Australian Government). To see some lovely images of these creatures, including free-swimming forms, have a look here: https://www.google.com.au/search?q=p...w=1501&bih=776

Cheers
KarlB

PS I too am a non-practicing marine biologist.