The Scorpio Races

This is one of the books that is a Young Adult Beehive Nominee for 2013-14 and is written by Maggie Stiefvater.

Some race to win. Others race to survive.

"It happens at the start of every November: the Scorpio Races. Riders attempt to keep hold of their water horses long enough to make it to the finish line.
Some riders live.
Others die.
At age nineteen, Sean Kendrick is the returning champion. He is a young man of few words, and if he has any fears, he keeps them buried deep, where no one else can see them.
Puck Connolly is different. She never meant to ride in the Scorpio Races. But fate hasn't given her much of a choice. So she enters the competition - the first girl ever to do so. She is in no way prepared for what is going to happen.
As she did in her bestselling Shiver trilogy, author Maggie Stiefvater takes us to the breaking point, where both love and life meet their greatest obstacles, and only the strong of heart can survive. The Scorpio Races is an unforgettable reading experience."

Although this book is a little slow to begin, I did enjoy reading it. It did get a "mature reader" star by the Children's Literature Association Of Utah, probably because it does take about blood and gets a little grisly at some points.