A mottled sleeper that hangs motionless against roots and pilings, often belly upward.
A sleeper to about 15 cm, elongate and nearly cylindrical, dark brown to olive with irregular darker mottling and a scatter of pale flecks. The head is depressed and pointed with a distinctly concave profile between the snout and the eye, which gives the fish its name. The pelvic fins are separate rather than joined into a sucking disc, and that is what separates the sleepers from the gobies they are otherwise easily taken for.
The characteristic posture is to hang motionless in the water beside a mangrove root, a piling, a piece of debris or a stand of weed, held at any angle including head-down and fully inverted, with the mottling breaking the outline against the surface behind. From that position it takes small fish and shrimp with a short lunge. It moves rarely and by short glides, and it will hold while a diver comes to within half a metre.
Recorded through the Indo-West Pacific in coastal and brackish water, in mangrove creeks, estuaries and the silty shallows of sheltered bays, and it tolerates a wide range of salinity. It is a shallow-water animal and belongs to the first few metres of a dive rather than to the slope, which is one reason it appears in fewer photographs than its abundance would suggest.
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.