Philinopsis speciosa

Philinopsis speciosa is a predatory Headshield Slug, coming in a wide variety of colour schemes. Apparently correct identification is based on body configuration.

There was some controversy amongst the PADI professionals at the diving school as to whether Philinopsis cyanea is the correct name for them, but now we see that WORMS and Wikipedia have confirmed that it is a synonym for P. speciosa.