Poliwhirl, the Tadpole Pokémon. Its highly developed muscles allow Poliwhirl to move efficiently on land, plus making it more agile in water.
– Ash’s Pokedex
Poliwhirl is based on a tadpole, like Poliwag. But unlike Poliwag, it doesn’t really look like a tadpole to me; it looks too human-shaped and upright to be a tadpole. The swirly design on its belly used to swirl counter-clockwise in Red/Blue, but got changed to clockwise since. It also swirls in the opposite direction as Poliwag’s swirl.
In the Pokemon Adventure manga, Red has a Poliwhirl, which was his first Pokemon (as a Poliwag), before he even got a starter from Oak
Stat-wise, Poliwhirl is fast, which its Pokedex entry refers to. Its ability Water Absorb could be useful in battle. I had a Poliwhirl briefly in HeartGold, I used it as my HM slave, as well as my Pokemon catcher because it has Hynopsis. I remember fighting Suicune with it, and Suicune couldn’t do much to my Poliwhirl.