Wartortle is a bipedal, indigo-blue Pokémon similar to a turtle. It has brown eyes, a dark blue streak on each cheek, and two sharp teeth protruding from its upper jaw. It has three clawed fingers and pointed toes. Bluish white fur covers its long ears and tail. A brown shell with a pale yellow underside encases its body. A thick, white rim separates the upper and lower halves of the shell. As Wartortle grows old, its tail fur will darken, and it may have algae growing on its shell. The shell may also carry scars from past battles.
To maintain balance while swimming at high speeds, Wartortle moves its furry ears and tail. It can use the fur to store air for extended underwater diving. Its tail is a popular symbol of longevity, making it popular with the elderly. It hides in water when hunting and emerges to surprise its prey.
Even though Wartortle's ears are depicted lighter than its face in the official Sugimori stock art and most of its game sprites, the official promotional pictures usually have the ears the same color as its face.
Its design appears to be a stylized turtle. Its feathery tail is a reference to Japanese legends of the minogame (蓑亀), a turtle which lived for 10,000 years and grew a tail made of seaweed. The use of its tail to store oxygen seems to be a reference to certain turtles that breathe through their cloaca, placed near the tail.