The hagfish uses slime to protect itself from predators, according to Sea and Sky, an informational website about space and marine life. The slime is made of tiny fibers that make it thick and difficult to remove.
Although it is not a fish, Sea and Sky states that a hagfish is an eel-like sea creature covered with glands that can secrete a slime-like substance and is often called the "slime eel." The hagfish uses the slime to make a cocoon to protect itself. Sea and Sky states it is believed that this slime can suffocate predators by blocking the gills and suffocating them if they come in contact with the hagfish.