Kingdom at Sea — Jill Williamson

Part 4 of Jill Williamson's Epic Fantasy Series The Kinsman Chronicles

When the ocean swallows their homeland, the survivors of five nations take to the ocean to look for new land, but their common plight isn't enough to stop the growing war between them.
 
As King Echad's illness worsens, Sâr Wilek takes authority over the expedition and struggles to rule the disjointed people while Prince Trevn sets his sights on learning to captain a great ship. Meanwhile, no one knows that Charlon and the Magonian Chieftess are on board in plain sight, plotting their takeover of Armania.
 
 Kingdom at Sea is collected together with parts 5 and 6 in King's Blood.