Swims head-down in a school, keeping vertical whatever the current does.
A fish to about 15 cm, flattened side to side to the thickness of a blade and enclosed in transparent bony plates, with a long tubular snout, a dark stripe running from snout to tail and a sharp keeled belly edge. The dorsal fin is not on the back — it sits at the rear end, because the whole fish is carried tipped nose-down.
Schools of a dozen to a hundred hang head-down and hold that orientation regardless of current, moving in unison by sculling with small fins. Nose-down against the vertical lines of seagrass, or among the spines of a Diadema urchin, the shape and the stripe disappear, and juveniles in particular use urchins as cover. Feeding is done by sucking small crustaceans through the tube snout. Recorded from the shallows to about 25 m. A school will let a diver come very close if the approach is made at their own angle, and will tilt as one to keep the thin edge presented.
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.