Is an eel a fish?

Electric eels aren’t neither are wolf eels but moray eels are. So what’s the difference? The easy answer is that a true eel is a member of the fish order Anguilliformes while other eel-like animals are not. Differentiating characteristics include a dorsal fin that is continuous with the caudal and anal fin and very small, embedded scales or no scales at all. A little known fact about morays is that they are sometimes recruited by Coral Groupers to help them while hunting for food. This is the only known instance of interspecies cooperation among fish.

Sometimes mistaken for eels there are 62 species of sea snakes and all are venomous. They are found in tropical waters of the Indo-Pacific and on average can grow to around four to five feet. As they do not have gills they must return to the surface to beathe although they can remain submerged for up to eight hours. The sea snake's body is flattened laterally and its oarlike tail is used as a scull.

Placid by nature they are not regarded as dangerous to divers but they do need respect as their venom can be up to ten times more powerful than that of a rattlesnake or the deadly black mamba. You don't want to meet one in a bad mood. They can be quite curious and sometimes attracted by their own reflections in the glass of an underwater photographer's camera housing port. I discovered this when one diverted its attention from hunting and started swimming directly towards me.  Finning backwards I wafted my fin directly over its head and only then, thankfully, did it seem to think that I was not worth the effort and returned to its hunting.