Yellow box fish

In this photo is the adult.
The Yellow boxfish, Ostracion cubicus, is a boxfish of the genus Ostracion, and can be found in reefs throughout the Pacific Ocean and Indian Ocean as well as the south eastern Atlantic Ocean. It reaches a maximum length of 45 cm.

As the name suggests, it is box shaped. When juvenile, it is very bright yellow in color. See my spotting:
http://www.projectnoah.org/spottings/6282189

As it ages, the brightness fades and very old specimens will have blue-grey coloration with the faded yellow. It feeds mainly on algae, but will also feed on sponges, crustaceans and mollusks.