The term "human fish" commonly refers to the olm, a unique amphibian found in the underground rivers and caves of Slovenia and other parts of Europe. This creature is notable for its pale, almost translucent skin and its ability to live in complete darkness. The olm can grow up to 30 centimeters long and has a lifespan of over 100 years. Olms are fully aquatic and possess external gills, which allow them to breathe underwater. They are adapted to their cave environment, with reduced eyesight and a keen sense of smell. The olm is an important species for studying evolution and biodiversity in subterranean ecosystems.