Morays do themselves no favors as far as putting divers at ease around them. In order to pass water through their gills, they open and close their mouths constantly like a snapping dog. It may appear they are interested in tasting you, when in fact they are more interested in smelling you. A fish's sense of smell is much more sophisticated than ours, and moray eels top the list. They can smell things we can only taste.
Fish give off unique pheromones that a moray uses to determine the size and type of another fish.
Two nasal canals on each side of the head pass water over sensitive cells that detect the presence of a potential meal, allowing the moray eel to hunt at night. Eels eat invertebrates, fish, and other eels. They can locate sleeping fish tucked into crevices by smell alone, one of the reasons parrotfish wrap themselves inside smell-trapping cocoons. The eel's other secret weapon is its ability to move backwards, as few fish can do this. To make reversing possible, eels have very small scales covered in mucus and do not have gill covers that would snag on objects.