Electric blue legs banded in black, with orange eyestalks, on shallow rubble.
A small hermit crab to about 3 cm, with bright blue walking legs crossed by narrow black bands, orange eyestalks and dark brown-black claws with a granular surface, the left claw the larger. The blue varies between populations from a hard electric blue to a greener shade, but the combination of banded blue legs and orange eyestalks is not shared by anything else at these depths. The dwarf zebra hermit crab, Calcinus laevimanus, is the one to rule out: it has an orange and white face, a smooth broad white-tipped left claw and boldly banded eyestalks, and it is generally in shallower and more sheltered water still.
It lives on shallow rock, rubble and reef flats, frequently in the top few metres and into the surge zone, grazing algae and detritus off hard surfaces. It uses small gastropod shells, usually turban and nerite shells, and populations can be dense on a suitable rubble bank. It is active by day and largely indifferent to divers, carrying on feeding with a camera close, which is unusual among hermits here.
Depth is the practical limitation: it is a shallow animal, so it is mostly met on the way in, on the way out or on a safety stop rather than during the dive itself, and it is easy to swim past a bank holding dozens of them.
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.