Also known as slime eels, hagfish are primitive fishes. They have five hearts, no jaws, no true eyes and no stomach. They have poor vision but a very good sense of smell and touch.
Hagfish live in burrows on the seafloor and locate their food by smelling and feeling as they swim. They prey on small invertebrates living in the mud, as well as scavenging dead and dying fish. They are noted for their unusual way of feeding—they slither into dead or dying fishes and eat them from the inside out, using their "rasping tongue" to carry food into their funnel-shaped mouth.
Hagfish are notorious for their defensive slime. They secrete a sugar and protein matrix into the seawater. When expelled, it mixes with the saltwater and becomes a slippery slime. Protein strands within the slime make it extremely sticky.
Anything that finds its way into the ocean, whether it's tossed away as trash, washes off a beach or falls off a boat, may eventually make its way to the deep sea. It's important to realize that the deep sea is not so far away that it's beyond the reach of human activities. Living creatures in the deep are affected by what we do at the surface.
Some so-called "eel-skin" wallets are actually made from hagfish.