These unusual grey Nanaimo nudibranchs (Acanthodoris nanaimoensis) are apparently genetically identical to the more common white form with maroon-tipped rhinophores (sensory organs) and gills. The dark phase of this nudibranch may be brown or brownish-grey in colour. It was a surprise for me to see this darker colour phase for the first time, as I usually see the lighter variety while diving. Very long papillae covering the oval body of this nudibranch give it a fuzzy appearance. Nanaimo nudibranchs can grow to 1.5 inches (4cm) in length, with a range from central Alaska to southern California.