The body translucent orange brown with green pigments, covered with low rounded tubercles, each surrounded by a dark green ring. Green rings forming a reticulate pattern all over the body. Seven finely branched gills on each side of the dorsum.
This dendronotid nudibranch grows to about 5,0 cm long. Marionia hawaiiensis feeds exclusively on the Hawaiian endemic blue Octocoral Sarcothelia edmondsoni. Marionia hawaiiensis is endemic to Hawaii.
Marionia hawaiiensis is common in shallow rocky areas among Sarcothelia edmondsoni.