Pacific Hagfish

Primitive fishes, hagfish live in burrows on the seafloor and locate their food by smelling and feeling as they swim, since they have poor vision but a very good sense of smell and touch. They prey on small invertebrates living in the mud, as well as scavenging dead and dying fish. They’re 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—a mucous fluid secreted from their pores. It’s different from slime that some other fish produce; millions of microscopic threads run through it, which makes it extremely sticky.