Body depth less than head length, body depth contained 2.6 to 3.0 times in standard length (for fish 10 to 19 cm standard length). Head length contained 2.3 to 2.7 times in standard length; preorbital depth usually less than half maxilla width, 2.5 to 3.6% of standard length; interorbital area flat; preopercle rounded, very finely serrate; no enlarged spines at angle, the lower edge fleshy; subopercle and interopercle weakly serrate; maxilla naked, reaching about to vertical at rear edge of eye. Gill rakers 7 to 9 on upper limb, 14 to 17 on lower limb. Dorsal fin with IX spines and 15 to 17 rays; the membranes indented between the spines; anal fin with III spines and 8 rays, the second spine 15 to 18% of standard length, reaching past tip of third spine; pectoral-fin rays 16 or 17; pectoral fins longer than pelvic fins, pectoral-fin length contained 1.3 to 1.6 times in head length; pelvic fins usually reaching to or beyond anus, pelvic-fin length contained 1.7 to 2.2 times in head length; caudal fin well rounded. Body scales ctenoid, without auxiliary scales; lateral-line scales 46 to 51; lateral-scale series 86 to 100.
Colour: Dark brown (occasionally dark reddish brown), usually with 7 or 8 dark bars on body; some fish with dark brown bands radiating from eye; black spot between upper and middle opercular spines; soft dorsal, anal, and caudal fins darker distally, with a pale bluish line on the edge (except central part of caudal fin).

C. boenak is primarily continental in its distribution, occurring from Kenya to southern Mozambique and eastward to the western Pacific (Ryukyu Islands Taiwan, China, Philippines, Indonesia, Papua New Guinea, New Caledonia, and eastern Australia). It has not been reported from oceanic islands in the Indian Ocean, except for Aldabra, Madagascar, and the Comoro, Andaman, and Lakshadweep islands. The record from the Seychelles (Smith and Smith, 1963) is apparently erroneous, the illustrated fish being from Delagoa Bay (Mozambique). It is not known from the Red Sea, Persian Gulf, nor the islands of Micronesia or Polynesia, except for Palau.

C. boenak is usually found in 4 to 30 m on silty dead reefs in protected waters; also taken in trawls to depths of 64 m. According to Myers (1989), it feeds primarily on crustaceans. Donaldson (1989) observed courtship and pair spawning at Papua New Guinea.

Maximum total length 26 cm.

Before 1984, most authors referred to this species as C. pachycentron, and the name C. boenak (usually spelt boenack) was erroneously applied to the bluelined hind (C. formosa). The latter differs in colour pattern and in having a shorter second anal-fin spine (12.0 to 14.6% of standard length, not reaching past tip of third spine) and the preorbital depth is more than half of the maxilla width. The holotype of Serranus boelang Valenciennes, 1828 is not (as listed by Bauchot et al., 1984) in the Muséum National d’Histoire Naturelle in Paris; it is a dry stuffed specimen, 142 mm standard length (RMNH 120) in the Rijksmuseum van Natuurlijke Historie, Leiden and appears to be a specimen of C. boenak.