The Amazonian Giant Leech is one of the largest leech species, reaching up to 18 inches in length. Found in the murky waters of the Amazon, this bloodsucker can attach itself to a variety of animals, including humans, using its sharp teeth to pierce the skin. What's even more unnerving is that the leech can suck up to ten times its body weight in blood. It also has a unique ability to detect prey by sensing movement in the water. Its size, feeding habits, and parasitic nature make this a truly strange and unsettling creature.