This is a hard nudibranch to spot, as it is often on its host sponge (or very close by) making it virtually disappear into the orange sponge-covered landscape.  Their relatively small size and three small crater-like depressions mid-notum don’t help.  These two animals were found in about 2 metres of water on an orange sponge-covered shelf of a large leaning rock outside of the Ke’ohe Fishpond, North Kihei.  Mature animal about 1″ or 25 mm.  Younger one was 6 mm or 1/4.”  There is a strong resemblance between the Aldisa pikokai and the Aldisa sp.#1 — a full discussion regarding the subtle difference can be found on Sea Slugs of Hawaii.