Hagfish

  There are many different species of hagfish, a primitive fish. Although technically scientists are still debating whether hagfish are actual fish. Hagfish are also sometimes called "slime eels", because of their ability to secrete slime. Hagfish are the only living animals with a skull but no vertebral column. The earliest fossil record dates back approximately 550 million years ago, in the Lower Cambrian Period.
  The hagfish is on average about half a meter or 18 inches, the largest specimen was recorded at 127cm. Hagfish have long, bodies, and paddle-like tails. The hagfish only has simple eyespots that can only detect light and dark. Hagfish have no fins and have a single nostril. They have an unusual pair of horizontally moving structures with tooth-like projections for pulling off food. The mouth of the hagfish has two pairs of horny, comb-shaped teeth that is able to protract and retract.
  As mentioned before, when the hagfish is caught by a predator, it can secrete a gelatinous, coat of mucus that expands into a sticky goo when combined with water, as seen in the video below. It removes any residual slime from the body by forming itself into a overhand knot and scraping the slime of the body. An adult hagfish can secrete enough slime to turn a 20 liter or 5 gallon bucket of water into slime within a matter of minutes.