This anime has since been re-reviewed in a more comprehensive & detailed manner via Retrospect in Retrograde, which you can read at this link.
The original Monkey Turn manga by Katsutoshi Kawai debuted in Weekly Shonen Sunday back in early 1997 and ended in early 2005 after 30 volumes. In fact, in 1999 the manga tied for the fairly prestigious Shogakukan Manga Award in the shonen category; the other manga it tied with was Weekly Shonen Jump's Hikaru no Go, and anyone who has read or watched HnG knows how excellent of a title it is, so co-winning an award like that is no small feat. The anime ran in 2004 from January to June, lasting 24 episodes, and while I don't know how much of the manga the show covers I will say that it is definitely one of the best sports anime that you've never seen.
Kenji Hatano is a baseball player with dreams of being a big star in the sport. Unfortunately, he doesn't like the fact that one person's mistake can make the entire team suffer. After meeting with the Principal of the school Kenji is taken to a kyotei (mini-hydroboat) race and witnesses one of the racers perform the Monkey Turn, a type of turn that only high-level racers can do. Feeling that it's easy to perform, Kenji gives it a try, almost making it but capsizing in the end. The thrill inspires Kenji to take up kyotei racing and after two years he graduates from a kyotei training school. He's so psyched to finally go pro that he promises his childhood friend Sumi Ubukata that he'll become Japan's top kyotei racer within three years, which is generally considered nigh-impossible by the pros. Of course, during his time at the training school Kenji also found a rival in Hiro Doguchi, whose father is a high-ranked kyotei racer. Now having graduated from the school, Kenji & company are ready to try their hands at the professional level.