The spotted boxfish is the most common boxfish in Hawaii. They really are little boxes with a hard carapace. Only their fins, eyes and mouth move. They can also secrete a toxic slime if they’re bothered.
Surprisingly, given their shape, they’re very good swimmers and can easily outdistance a human. Such is their prowess in this regard that they’ve served as inspiration for submarine and car designs.
On a more basic level, they’re always fun to see in the water, puttering along nimbly, and keeping a good distance ahead of pursuing photographers. The top boxfish is a male and the one on the left, a female.