Projects its jaws half a head-length forward in a fraction of a second.
To about 54 cm. Terminal males are dark brown-grey with a white head and a yellow-orange body patch; females and initial-phase fish are plain yellow or dull brown. All phases have a distinctive pointed profile and a long body. The identifying feature is not visible until it feeds: the jaws are mounted on an extendable framework and shoot forward about half a head length to engulf prey, faster than the eye follows.
It hunts small fish and crustaceans in coral branches and crevices, easing up to within range before firing. Watching it work a coral head is where the mechanism becomes visible, and a strobe-lit sequence will catch the extension that the eye cannot. Sex change from female to terminal male is accompanied by the full change of colour. Recorded from about 2 to 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.