River of the World

Maras-Sund has stood for more than twenty years, the two cities joined as one, bound together by an otherworldly bridge erected by the Marasi. With their own magic over the water diminished by their overlords, the Sundain's only hope for liberation lies with a man of limitless but untested power ...
Possessing an affinity for water unparalleled by any of his people, Issel has led a small band of resistance fighters across the river from Sund to Maras in an attempt to break the magic binding the lands. Hunted by enemy soldiers, they've taken refuge in the cistern network beneath the city where they can travel unnoticed and strike without warning. But surrounded by so much water, Issel finds his abilities threatening to tear him apart - body, mind, and soul.
The rebels find an ally in Jendre, the daughter of a general in Maras's army, and someone with her own vendetta against the regime. Her sister is held captive, along with others whose life essences power the magical bridge between her land and Sund. Under other circumstances they would have been enemies. But in these extreme times, Issel and Jendre are the last hope of their two suffering peoples.