Grunion bluish-green backs and silvery sides and bellies. Their snouts are bluntly rounded and slippery. Silversides differ from true smelts of the family Osmeridae in that they lack the trout-like adipose fin. Young grunion grow rapidly and are about five inches long by the time they reach one year old and are ready to spawn. Adult fish normally range in size from with a maximum recorded size of (La Jolla, Ca., 05-11-05). Average body lengths for males and females are , respectively, at the end of one year; at the end of two years; and at the end of three years.
USS Grunion the exact location indicated by the commander of the "Kano Maru". The sunken object had many characteristics typical of a submarine. In 2007, using a ROV, DSSI/Oceaneering returned to the site and took video recordings of the imploded remains of a submarine, which had markings in English, and propeller guards and limber holes identical to those of the "Grunion". The following year, the US Navy confirmed that the find was the "Grunion". Although it is not absolutely certain, the evidence strongly suggests that the "Grunion" was lost as a result of multiple torpedo failures during her encounter with the "Kano