Water bears are actually some of the toughest forms of life.
although i don't think they could be to blame for biting a person in half
Tardigrades can survive in extreme environments. For example, they can withstand temperatures from just above absolute zero to well above the boiling point of water (100°C), pressures about six times greater than those found in the deepest ocean trenches, ionizing radiation at doses hundreds of times higher than the lethal dose for a human, and the vacuum of outer space. They can go without food or water for more than 10 years, drying out to the point where they are 3% or less water, only to rehydrate, forage, and reproduce.[3][6][7][8] They are not considered extremophilic because they are not adapted to live in these conditions. Their chances of dying increase the longer they are exposed to the extreme environments,[5] whereas extremophiles are organisms that can thrive in a physically or geochemically extreme condition that would be detrimental to most life on Earth.