The Mediterranean moray eel (Muraena helena) is a benthic anguilliform fish that can grow to over 1 meter in length and is a characteristic species of rocky infralittoral habitats throughout the Mediterranean Sea. It has an elongated, snake-like body without visible pelvic or pectoral fins, giving it the typical finless appearance of moray eels. Its colouration is generally dark brown with yellowish speckles, which helps it blend into rocky crevices and shaded reef environments. Another distinctive feature is the presence of tubular anterior nostrils, a diagnostic characteristic of the genus Muraena.

This species typically occupies permanent shelters within crevices, holes, and cavities in rocky substrates, ranging from very shallow waters to the circalittoral zone. The Mediterranean moray eel shows strong site fidelity, often remaining in the same refuge for long periods. It is mainly crepuscular and nocturnal, emerging from its shelter at dusk or during the night to hunt. During the day, it usually keeps only its head protruding from its refuge with its mouth open, a behaviour that facilitates gill ventilation. Although this posture is sometimes mistaken for aggression, it is simply a normal respiratory behaviour.

For snorkellers and divers, it is important to note that the Mediterranean moray eel is generally not aggressive. It shows territorial but non-offensive behaviour, and incidents usually occur only if the animal is provoked or handled. At night, however, encounters are more frequent as the moray actively hunts. As a mesopredator within rocky ecosystems, it feeds primarily on fish, crustaceans, and cephalopods, playing an important role in maintaining the balance of coastal marine communities.