Trunkfish
Trunkfish, or Boxfish, the common names for a family of fish whose members are found in shallow waters of warm seas around the world. These fish are so named because the head and most of the body of the adult are enclosed in a boxlike structure of bone. The box is so rigid that trunkfish can move only their fins, eyes, mouth, and tail.
There are about 20 species of trunkfish, including the cowfish, the blue boxfish, the gray boxfish, and the spotted trunkfish. Trunkfish are small, the largest species growing to about 20 inches (50 cm). They are colorful fish with bright patterns of such colors as blue, red, white, and black. Some species are capable of changing their color.
Trunkfish make up the family Ostraciidae.