Yellow boxfish (Ostracion cubicus) also often called yellow trunk fish, are solitary animals. Breeding occurs during the spring, in small groups that consist of 1 male and 2–4 females.
As the name suggests, it is square-shaped. Boxfish are also known for their armored and rigid body, which in most cases would inhibit movement. Due to its adapted swimming style, known as ostraciform locomotion, this disadvantage is compensated for by the shell shape of the boxfish and is even more advantageous.