The African longfin eel[3] (Anguilla mossambica), also known simply as the longfin eel, is an eel in the family Anguillidae.[4] It was described by Wilhelm Peters in 1852, originally under the genus Muraena.[5] It is a tropical eel known from freshwaters in southern Kenya, Cape Agulhas, Madagascar, and New Caledonia. The eels spend most of their lives in freshwaters far inland, but migrate to the Western Indian Ocean to breed. Males can reach a maximum total length of 150 centimetres; females can reach a maximum standard length of 120 centimetres and a maximum weight of 5,000 grams. The eels can live for about 20 years.[4] Juveniles and adults are known to feed off of carcasses, crabs, and bony fish.[6]

The Zebra Moray Eel has a body pattern of alternating black and white stripes. It commonly lives in the coral reefs of the Indo-Pacific region, including the Red Sea, Hawaii, and the eastern coast of Africa. The eel's teeth are shaped like molars, crushing crustaceans such as shrimp, crabs, and mollusks before eating them.

Despite its unique appearance and eating habits, this type of eel is peaceful. When approached by divers or snorkelers, it retreats to rocky shelters.

The freshwater habitats of New Zealand are home to the New Zealand Longfin Eel. These eels can grow up to 6.6 feet long, with females reaching this maximum size. Hence, the New Zealand Longfin Eel is one of the world’s largest eel species. 

These eels are olive green to brown. Their long dorsal fins are notable features; they undulate gracefully, helping them move quietly during nocturnal hunts. Despite their size, they are shy creatures.

During the day, they hide in shadowy locations, such as submerged logs or unseen crevices. Their keen sense of smell helps them find prey, primarily invertebrates, small mammals, and other fish.

Moreover, these eels can live for over a century but only breed once. During the breeding season, they embark on an epic journey from their freshwater homes to their spawning grounds in the deep Pacific Ocean near Tonga. After mating, the eels die. Then, thousands of minute larvae return to New Zealand, guided by the waves.

The speckled longfin eel, Australian long-finned eel or marbled eel (Anguilla reinhardtii) is one of 15 species of eel in the family Anguillidae. It has a long snake-like cylindrical body with its dorsal, tail and anal fins joined to form one long fin. The dorsal fin also often extends farther than the anal fin. It usually has a brownish green or olive green back and sides with small darker spots or blotches all over its body. Its underside is paler.[2] It has a small gill opening on each side of its wide head, with thick lips. It is Australia's largest freshwater eel, and the female usually grows much larger than the male.[2][3] It is also known as the spotted eel.

The Southern Shortfin Eel typically inhabits cooler freshwater areas in Australia, New Zealand, and Tasmania. This species is dark brown and olive green, with a lighter underbelly and a shorter dorsal fin. Due to their snake-like locomotion, they can briefly go on land.

The Southern Shortfin Eel also starts life in the deep Coral Sea, turning from larvae into transparent glass eels. Braving numerous challenges, these eels journey from their birthplace to freshwater habitats. Female eels are larger than males, growing up to 3.3 feet long.

These types of eels prefer to stay hidden during the day under rocks and vegetation. They are active at night, feeding on fish, crustaceans, insects, and worms.

The purple spaghetti-eel[2] (Moringua raitaborua) is an eel  in the family Moringuidae  (spaghetti/worm eels).[3] It was described by Francis Buchanan-Hamilton in 1822, originally under the genus Muraena.[4] It is a tropical eel known from India, Bangladesh, Nepal, Indonesia, and the Philippines. It inhabits rivers  and estuaries (including ones in West Bengal, linked to the Ganges River), and has adapted to rapid and wide changes in salinity, pH, and osmoregulatory and hypoxic conditions.[5] Males can reach a maximum standard length of 44 cm.

Snake eels or worm eels look like snakes with long bodies and a scaled texture. They range in color from brown to bright hues and often have patterns serving as camouflage. They live in marine, brackish, and sometimes freshwater environments and spend most of the day burrowed in sand or mud. 

This type of eel has a forward escape technique—they disappear by moving forward, not backward, into the sand. Additionally, their hard, pointed tails are uniquely adapted for burrowing. These traits showcase the fascinating adaptability of life underwater.

Pike conger eels can live in fresh and saltwater environments, although they typically prefer saltwater. These eels can grow from two to eight feet long and survive depths of up to 2624.67 ft.

Approximately fifteen different species of pike conger eels live around the world.

Sawtooth eels are pelagic fish living in the dark depths of the ocean. Their name comes from their inward-facing saw-like teeth. This type of eel comprises around eleven species; most sawtooth eels have a maximum size of 24 to 28 in.

Growing up to 5 feet, this long, slender eel moves quickly through the rocky reef environment. The Mediterranean Moray Eel ranges from dark brown to soft grey, with a yellowish underbelly. It doesn't have pectoral fins.

This eel feeds on fish, squids, and octopuses. However, it's far from the top of the food chain as larger fish and marine mammals like seals and sea lions also prey on them.

Moreover, the Mediterranean Moray Eel forces water over its gills to breathe, requiring it to open and close its mouth rhythmically.