The green moray isn't actually green: its skin is brownish-grey, but a thick yellow mucus coating mixes with the blue skin tone underneath to create that greenish look. Its constant mouth-opening isn't a sign of aggression, it's simply how the eel pumps water over its gills.
What defines this group — Reef fish
The bony fish that live against coral and rock: the living backdrop of almost every dive.
A bony skeleton, scales, and a rigid gill cover closing over the gills.
A swim bladder acts as a float: they hold their depth without swimming.
Many change colour, pattern — sometimes even sex — over the course of their life.