Quagsire is a light blue, bipedal, amphibious Pokémon. Its head is broad and round, having little neck to distinguish it from the rest of Quagsire’s body. It has a wide mouth and tiny, black eyes. A wavy, purple stripe runs down its back. Quagsire’s hands and feet both have three digits. Its outer layer of skin is slimy and slippery.

From its introduction in Generation II until Generation IV, Quagsires generally had a lighter blue highlight on their hands and feet, a design implementation that was ultimately scrapped by Gen V. The last known occurrence of this design was used in the illustration of Quagsire GL, a card released in Platinum: Bonds to the End of Time in Asia and Platinum: Rising Rivals internationally.