Ugliest fish in the world

Hagfish are a primitive kind of eel-shaped slime-producing marine fish. They are sometimes called slime eels because of that. They are the only known living animals that have a skull but no vertebral column. Hagfish average about half a meter in length. The skin is naked and covers the body like a loosely fitting sock. Hagfish are long and can exude copious quantities of a milky slime. When captured and held, e.g., by the tail, they secrete the slime, which expands into up to 20 litres of sticky, gelatinous material when combined with water. They are also quite ugly and so deserve to be included here.