The juvenile is a bright yellow dice with black spots; the adult is not.
The juvenile is almost exactly cubic, two to three centimetres on a side, brilliant chrome yellow with round black spots, and it is one of the most photographed small fish in the Indo-Pacific. The adult reaches about 45 cm, loses the cube shape for a longer wedge, and fades through olive and grey-blue to a dull brown-yellow with pale-centred spots; large males take on blue flanks. The two stages are so unalike that divers routinely do not connect them.
The body is enclosed in a rigid carapace of fused bony plates with openings for the fins, mouth and vent, so the fish cannot flex and swims entirely by sculling with small fins — slow, deliberate and unbothered. The armour and the skin toxin between them buy that. Juveniles shelter in rubble and around jetty pilings and are strongly site-attached, so one found on a dive is usually still there a week later. Recorded from the shallows to about 40 m.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.