Slender silver fish held just under the surface, the lower jaw drawn out into a long beak.
A slender silver fish held horizontally a few centimetres below the surface, the lower jaw drawn out into a long straight beak and the upper jaw short and triangular. The back is green to blue, the flank carries a silver stripe, and there is no adipose fin. The tail is forked with the lower lobe the longer, which suits a fish that spends its life against the surface film. Most animals seen over muck ground are between 10 and 25 cm.
Halfbeaks hold station in loose groups over shallow sand, along the edges of mangrove and around jetty pilings, feeding on small animals and floating material at the surface and taking drifting weed. A group disturbed from below scatters and skitters across the surface rather than diving. The estuarine halfbeaks of Zenarchopterus, the ones most often over sheltered muck shallows, bear live young rather than shedding eggs into the water.
Species are separated on beak length, fin ray counts and details of the male anal fin, none of which is readable from directly below through a moving surface, so records here are kept at the family. The group belongs to the safety stop and to the last few minutes of a shore entry rather than to the dive proper, which is why halfbeaks appear in far fewer photographs than the number of times they are passed.
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.