Qwilfish resembles a pufferfish. It has a Bluish Greenish top, and a pale underside. Noticeable features of Qwilfish are its toxic spikes, its paddle-like tail, and its round shape. In Pokémon Diamond and Pearl, you can catch it out in the water you can get to out of Iron Island. And its eyes are straight and serious.
Bold indicates this Pokémon receives STAB from this move. Italic indicates an evolved or alternate form of this Pokémon receives STAB from this move.
Despite it's reputation as a bad swimmer, it is able to learn the HM moves Surf, Dive, and Waterfall and one of its abilities is Swift Swim.
In an early design for what would became Qwilfish (Japanese: ハリーセン Harysen), it was called Bukū, which was possibly a corruption of the word fugu (河豚, meaning "river pig"), which both are the Japanese word for pufferfish and the dish prepared from it.