Water bear. Coloured scanning electron micrograph (SEM) of a freshwater water bear (Echiniscus sp.). Water bears, or tardigrades, are tiny invertebrates that live in coastal waters and freshwater habitats, as well as semi-aquatic terrestrial habitats like damp moss. They require water to obtain oxygen by gas exchange. In dry conditions, they can enter a cryptobiotic tun (or barrel) state of dessication to survive. Water bears feed on plant and animal cells and are found throughout the world, from the tropics to the cold polar waters.