The elongate head bears a large, gaping mouth and tube-like nostrils. The mouth is held open so that water can be pumped over the gills. The gill cover is reduced to a small hole for streamlining and protection of the delicate gills. Lacking paired fins, eels swim by moving their entire body side to side in a S-shaped wave. Using this wave pattern an eel can move forward or backward, an important advantage if living within the narrow holes of the reef.
Morays lurk in holes and crevices in rocky areas or on the coral reef.
During the day, often only the head is visible at the entrance to its shelter, but most eels are never seen. They usually emerge at night to search within and over the reef for prey which they locate using a keen sense of smell. There are two major groups of moray eels in Hawai i, differentiated by the kind of prey they are adapted to take. Their teeth curve backward so that once captured, prey cannot escape and can be moved more easily backward for swallowing. While armed with formidable teeth, most moray eels are not usually aggressive and will not attack prey larger than themselves.