Rain Wild River
From PlentyWiki
The disputed western border of Chalced. Once known as the Serpent River. In the Six Duchies it is called Rain River.
The river's water is highly acidic. Usually it is acidic enough to slowly dissolve wood or leather, but in the aftermath of quakes, the acidity increases dramatically. The water runs white and can eat swiftly through flesh.
The liveships are the only known vessels that can reliably survive the acid waters.