[4] Nudibranchs, an order of opistobranchs or sea slugs, are a diverse group of marine gastropods known for their bright coloration and unique morphologies.

Generally, nudibranchs are carnivorous and their specialized radula enables them to feed on a variety of prey, including sponges, hydrozoans, bryozoans, and various species of coral.

Its cerata are translucent white with brown pigmentation, which is caused by aggregations of unicellular dinoflagellate (known colloquially as zooxanthellae), and are held laterally, giving it a very flattened appearance.

The jaws of this species have smooth cutting edges, featuring broad teeth that lack a central cusp, with 8–12 denticles on each side of the median area.

This species has been observed holding its cerata in a characteristic S-shape or at right angles, which maximizes its cryptic ability on the host coral.

[4] These sea slugs feed exclusively on Pavona explanulata, a species of encrusting coral that commonly develops massive and sub-massive irregular domes.

[4] Like all sea slugs, Phestilla viei are hermaphrodites, meaning that they have male and female reproductive organs and can produce gametes associated with both sexes.

The female gland mass measures around 2 millimeters in length and is attached to the ampulla, which in turn is connected to the oviducts.