Grey, yellow or almost black depending on the fish, and lethally toxic to eat.
A puffer to about 33 cm with a blunt rounded head and a heavy-lidded expression that has earned it the dog-faced name. Colour is extremely variable — pale grey, dark charcoal, powder blue, or a bright yellow form with a grey face — and all forms carry scattered small black spots and a dark ring around the eye and the pectoral base. The jaw is a fused beak of four plates used to crush coral, molluscs and crustaceans.
Puffers do not manufacture tetrodotoxin; they acquire it from bacteria through the food chain and concentrate it in the skin, liver and gonads, which is why farmed fish raised on clean feed are far less toxic. The dose in a wild adult is enough to kill an adult human and there is no antidote. Inflation is a defence of last resort and stressful for the fish — a puffer inflated for a photograph is a fish that has been harassed. Recorded from the shallows to about 30 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.