There are actually very few types of scaleless fish, particularly salt water scaleless fish. Typically, these species cannot tolerate salt water very well, but there are some exceptions. For the most part, the scaleless salt water fish resemble snakes, with the sea catfish being the exception. Some of the other scaleless salt water fish include the moray eel, sea lamprey, and Atlantic hagfish.
According to the National Wetlands Research Center, sea catfish are typically found in "Atlantic coastal waters from Cape Cod, Massachusetts, to Yucatan, Mexico." The fish is characterized as being scaleless and having serrated fins, as well as being gray-blue and silver in color. It also produces a mucus on the outside of its body, which causes it to be very slimy.
The moray eel is one of the few scaleless eels, which are in fact fish. Typically eels have very small scales that are almost invisible, the moray eel however has no scales and its soft skin is covered in a slimy mucus to protect it. The moray eel resembles a snake, and is light greenish-yellow. Moray eels have very small eyes, making them almost blind, but they do have incredibly sharp teeth to make up for it. According to Roundhouse Aquarium, "Moray eels eat a variety of fishes, octopuses, crabs and shrimp." Like other eels, the moray eel prefers to live in coral, rocks, and caves.
The sea lamprey is known as an ocean parasite. These animals feed on other fish by attaching their round teeth filled mouths on to the sides of the fish, then burrow out holes. The lamprey is another scaleless fish that closely resembles a snake. According to Marine Bio, "the sea lamprey...is found only in the Mediterranean and North Atlantic, in the coastal seas off the North East USA, Nova Scotia, southern Greenland, the UK, Ireland and Scandinavia. It is also found in the Great Lakes." Sea lampreys typically range from blue to black in color and have no paired fins.
The Atlantic hagfish, also known as a slime eel, is another salt water scaleless fish. According to Sea and Sky, "the Atlantic hagfish is a deep-water fish. They can be found at depths of up to 5,600 feet...They are known on both sides of the North Atlantic Ocean as far north as Norway." The hagfish is able to secrete a very sticky, slimy mucus from its skin, which it uses to protect itself from would-be predators. The hagfish is almost completely blind, but has a heightened sense of smell and touch, with small feelers located around its mouth. They vary in coloring, but are typically pink, brown, or gray.