Arabian angelfish

The Arabian angelfish (Pomacanthus asfur) looks like its yellowbar cousin switched to night mode: the body is a deep, almost black blue, cut by a sharply glowing vertical golden crescent, and the tail is brilliant lemon yellow. That tail is the surest field mark – the similar yellowbar angelfish has a duller, marbled tail. The species is a speciality of the Red Sea and Gulf of Aden region, appearing elsewhere in the world only as a stray.

While its big relatives cruise open plateaus with confidence, the Arabian angelfish is decidedly shy: it favours densely coral-grown, sheltered walls, hollows and quiet bays, and retreats deep into crevices at the first suspicious move. It lives mostly alone, grazing on sponges, tunicates and algae. Juveniles wear a disguise here too: their dark-blue bodies with pale blue-and-white stripes are almost identical to young yellowbar angelfish.

Around Hurghada it is a scarcer treat than the yellowbar, which is exactly why divers celebrate each sighting: search the recesses of sheltered wall sections and the shade of overhangs, typically between 5 and 25 metres. Patience is the key: hold position a few metres off the wall, wait quietly, and the curious fish will eventually venture out – its yellow tail flashing in the blue gloom like a lantern.