I found this nudi at around 12m (35 ft) depth on the island of Sangeang, Indonesia at the divesite Hot Rocks. Its size is probably around 2 to 5 cm long. I'm thinking it's likely a Phestilla. In this small area of reef I found at least 10 individuals, but most of them were tightly clustered together feeding and/or laying eggs on their hard coral host. I haven't found it in any ID books that I've had available and I can't find it on Seaslugforum (which is inactive anyway) any ideas? if an ID can be made of the hard coral from these images, that would be handy too.
Two different shots of individuals:
A closer shot of one of the clusters:
Eggs:
Amazing camouflage
It's definitely a Phestilla; perhaps Phestilla sp. 2 in Indo-Pacific Nudibranchs and Sea Slugs. Here is a similar one:
I didn't see that one (it's really impressive), but I had trouble with this one (I had to resort to labelling it as a "fractal" nudibranch!), also from Sangeang in September:
