A hydrozoan, not a coral, growing as a net of fused blades on the shallowest reef, where surge puts people into it.
Colonies to about 50 cm, mustard to tan with pale tips, growing as a net of fused vertical blades on shallow reef and the reef crest. The blades meet and join, which is what separates it from the branching fire coral, and the shape is genuinely reticulate rather than antler-like.
It is a hydrozoan, not a true coral, and the fine hair-like polyps carry the stinging cells. It grows in the shallowest, roughest water on the reef, where a diver or a snorkeller is most likely to be pushed onto it by surge, and the sting produces immediate burning followed by a welt and days of itching. Vinegar on the skin, and do not rub it. In the Red Sea it is one of the commonest injuries reported by dive centres.
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.
