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.