Their name and shape!

Ostraciidae is a family of squared, bony fish closely related to the pufferfishes and filefishes. Members of this family occur in a variety of different colors (e.g. right - Hawaiian Blue Boxfish, Ostracion meleagris and the Yellow Boxfish, Ostracion cubicus), and are notable for the hexagonal or "honeycomb" patterns on their skin.

Boxfish swim in a rowing manner. Their hexagonal plate-like scales are fused together into a solid, triangular or box-like carapace, from which the fins, tail, eyes and mouth protrude. Because of these heavy armoured scales, Ostraciidae are limited to slow movements, but few other fish are able to eat the adults.

Some boxfish also secrete poisons from their skin into the surrounding water, fu ...