An anemone, not a nudibranch!
Photo by Alistair Clacherty
A few more violet-spotted anemones
The dwarf spotted anemone (Anthostella sp.), in "normal" state.
The dwarf spotted anemone extended.
All other photos Guido Zsilavecz
This anemone, which is known to occur from Namibia to Richards Bay, has been observed to feed on purple soft coral (Alcyonium fauri). Many anemones feed by waving their tentacles in the water and simply grabbing whatever comes their way, with the hope that it is nutricious. The violet-spotted anemone cannot do this when trying to get purple soft coral, because the coral is sessile and doesn't just float by. To compensate, this anemone uses the trick of extending itself and simply leaning over until it finds some soft coral, which it then devours. As can be seen from the photos, this results in rather odd-looking anemones.
It has a close relative, the dwarf spotted anemone (which is visually similar - but has the violet spots in rows, not randomly scattered, along the column), which is able to do this even better, extending itself to a thin but long body.
For more details on these anemones, see "A field guide to the Marine Animals of the Cape Peninsula", by Georgina Jones, now available directly from SURG or better Cape Town dive and book stores.
A field guide to the Marine Animals of the Cape Peninsula, G Jones, 2008
Two Oceans, A guide to the marine life of Southern Africa, GM Branch, CL Griffiths, ML Branch and LE Beckley, 1994.