The Tadpole Pokémon; Poliwag has a very thin skin. It is possible to see the Pokémon's spiral innards right through the skin. Despite its thinness, however, the skin is also very flexible. Even sharp fangs bounce right off it.

The surface of Poliwhirl's body is always wet and slick with a slimy fluid. Because of this slippery covering, it can easily slip and slide out of the clutches of any enemy in battle.