Comb jelliesCtenophora

Comb jellies are not jellyfish and not even close relatives. They are their own phylum, and they swim by beating eight rows of fused hair-like plates, the combs that give them their name. A torch beam scattering off those moving combs breaks into a running band of colour, which is the easiest way to spot one at night.

They have no stinging cells at all. Instead most species trail two long tentacles studded with sticky cells that hold small prey the way flypaper does, and comb jellies are voracious hunters of plankton for their size. The body is largely water, and a specimen brought into a bucket usually falls apart.

A handful of species gave up swimming altogether. The creeping comb jellies flatten themselves and crawl over soft corals, sponges and sea urchins, so far from the usual jellyfish outline that they were long mistaken for flatworms. They are the ones divers in this sea are most likely to find, if they look closely at the surface of a leather coral.