Dear Valda,
This is another mystery I'm afraid. It has a very similarly coloured cerata to a colour form of the janolid Bonisa nakaza that Gosliner (1981) illustrated from South Africa, but as you can see in the photo of Janolus mokohinau, janolids have cerata all around the front of the head and do not have the large prominent oral tentacles we can see in your photo.

It is clearly an aeolid, and from its size, arrangement of cerata, and relatively small rhinophores placed close together, it possibly belongs in the family Aeolidiidae. There are also a number of species of the aeolid family Cuthonidae with blue and yellow cerata, but none seem to fit your photo.

It also has similarities to Godiva quadricolor which also has large laterally pointing oral tentacles and relatively small rhinophores sitting close together in the midline. However, unless that species has a very wide colour variation, it seems an unlikely identification.

Hopefully Terry Gosliner will come to our aid.

Best wishes,
Bill Rudman.

Dear Terry,
I fully agree that it looks like a Cerberilla, which is why I suggested the family Aeolidiidae.

Valda, species of Cerberilla are usually found in sandy habitats where they live in the sand and are seldom seen. They have an unusually broad foot, presumably an adaptation to their sand-dwelling lifestyle. I will try and post a couple of pages on species of Cerberilla in the next few days.
Best wishes,
Bill Rudman.