Massed in the dark under a ledge, red and white, with a rostrum that folds up.
A shrimp to about 4 cm, deep red patterned with a network of clean white lines and spots, with a strongly arched back and large dark eyes. Its name is anatomical: the rostrum is hinged where it joins the carapace and can be raised and lowered, which no other shrimp a diver meets here can do. Males develop greatly enlarged first chelipeds and a longer rostrum with age.
Gregarious and light-shy. Groups of tens to hundreds pack into the darkest parts of overhangs, caves, wrecks and the undersides of jetty structure, and disperse out onto open surfaces at night to feed. A light swung into a crevice will show a wall of eyes before it shows any shrimp. Recorded from about 3 to 30 m. Because they are packed into a shaded space, the photographic problem is lighting a subject that is against a dark ceiling with no clean background — most of the workable frames are of one animal at the edge of the group rather than of the group.
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.