This is a NEW RECORD for Queensland and the Mooloolah River, found from under a rock.
Previously known from Tasmania and New South Wales and thought of as Onchidoris depressa which is from the Atlantic Ocean
and lays an egg mass with 2 rows per whorl. The animals from Australia lay a single row and must be Idaliadoris maugeansis.
Confirmed by Bob Burn

Below: in situ animal at bottom of the white bryozoan.

Below: the dorsal side of the animal is covered with long papillae

Below: the ventral side showing a large "oral veil" characteristic of the genus.

Below: closeup of the elongated papillae on the dorsum and rhinophores.