Warning: This educational video shows a leech sucking someone's blood out. I've never actually seen a leech in action until I came across this gnarly Leech Feeding Time-Lapse. The dude in the video voluntarily places a leech on his hand and records the critter growing plump with his blood. The bite mark it left was bigger than I expected.
Fun Fact: A single leech can drink about 5 to 10 ml of blood during a feeding, which is almost 10 times its own weight. Leeches a hundred teeth and three jaws. They also inject an anesthetic into the skin through their bite. Leech spit contains anticoagulants which stop the blood clotting, which is why the guy in the video bleeds so much once the leech is removed.
