Season 1 of Mizugi Kanojo: The Animation premiered on January 23, 2009.

The story begins with a pair of young lovers, the busty Mizuho-chan, and the well endowed Hiro-kun. One night Hiro suggests that Mizuho should try swimming to get in shape. He even offers to coach her after hours at the pool where he works since she can't swim very well. Mizuho's new workout plan turns out to be much more exciting than expected...

Meanwhile Takuya-kun finds himself in a compromising situation with his clumsy but beautiful neighbor Sayaka-chan...

Each episode features couples enjoying various sexual escapades involving plenty of water, wet bodies, & extremely revealing mizugi (swimsuits).