The Free! anime has been celebrating its 10th anniversary lately, and 2013 is when the swimmers of the series first hit the water. To mark this momentous occasion for the Kyoto Animation anime—which is based on the High Speed novel by Koji Oji—a celebratory visual made its way online.
The TV anime and the first two anime films are available to stream on Crunchyroll, which describes the series like so:
Nanase Haruka loved to be in the water – loved swimming. In elementary school, Nanase Haruka, Tachibana Makoto, Matsuoka Rin, and Hazuki Nagisa attended the same swimming class together. Time passed, and as Haruka was living an uneventful high school life, he suddenly encountered Rin again. Rin challenged Haruka to a race and showed him how much stronger he had become. Soon enough, Makoto and Nagisa also rejoined the group, and along with a new classmate, Ryugazaki Rei, they established the Iwatobi High School Swimming Club.
Via Crunchyroll News