Boxfish (Cofferfish)
Yellow boxfish (Derek Keats / CC BY)
Boxfish (Ostraciidae) are characterized by bony polygonal plates that give them the appearance of a box or suitcase. They have small mouths with conical, stout teeth. Boxfish are poor swimmers. Acanthostracion quadricornis can reach a length of 60 centimeters (24 inches). Most species are smaller, though. Ostracion lentiginosus and some other boxfish species secrete a highly toxic substance (ostracitoxin) when disturbed, so divers should avoid touching them.
Some species venomous.
This supplemental online resource accompanies the book Scuba Diving Hand Signals by Lars Behnke, available on
Amazon.