A large silver fish with huge scales and an upturned mouth, hanging almost motionless under bridges and in caves. It gulps air at the surface, which lets it survive water with very little oxygen.
To about 2.5 m, silver, deep-bodied and covered in scales the size of a coin, with an upturned lower jaw and a single long trailing ray off the back of the dorsal fin. Nothing else in the region looks like it. In a torch beam the flank returns the light like a mirror.
It gulps air at the surface and takes oxygen through a lung-like swim bladder, which lets it survive in water too poor in oxygen for most fish, and is why it is found in channels, canals, harbours and mangrove systems as well as on the reef. By day it hangs almost motionless in the shade under a bridge or in a cave, in ones or in a loose group, and lets a diver come close. At night it hunts, and at Blue Heron Bridge it works the edge of the light, which is where the photographs are taken. It is a very long-lived fish — individuals over fifty years old are documented — and it is almost entirely a catch-and-release sportfish rather than a food fish.
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.