Blastoise is a large, bipedal tortoise-like Pokémon. Its body is dark blue and is mostly hidden by its tough, brown shell. This shell has a pale yellow underside and a white ridge encircling its arms and separating the upper and lower halves. Two powerful water cannons reside in the top sides of its shell. These cannons can be extended or withdrawn and can be used to assist in high-speed charges. Blastoise's head has triangular ears that are black on the inside, small brown eyes, and a cream-colored lower jaw. Its arms are thick and striated with three claws on each hand. Its feet have three claws on the front and one on the back. It has a stubby tail.
As Mega Blastoise, it develops two smaller shells over its arms, each with their own water cannon. The two cannons on its back are replaced by a single, central water cannon of greater size. This cannon extends forward over Mega Blastoise's head and is said to have a blast range of over 6 miles. Small ridges develop over its, now red, eyes and extend to its ears. The ears angle slightly backward and there is a small point on its chin.
The powerful cannons on this Pokémon's back are capable of producing water blasts that can pierce steel and concrete. Blastoise deliberately makes itself heavy to withstand these powerful blasts, and it will crush its opponents with its bulk.