The Raccoon Butterflyfish (Chaetodon lunula) is named for the black and white stripe covering the eyes. It is just one of the many species of butterflyfish that are commonly found in mated pairs (although Raccoon Butterflies are also found in small schools during the day as shown in this photograph). One scientist (H.W. Fricke) has found that butterflyfish may stay in such mated pairs for three years, possibly even longer. 

This school was photographed in about 45 feet of water off the south Kohala Coast near Puako Beach on the Big Island of Hawaii.