Books of Arna Series by Christopher Rowley

Young watermot Thru Gillo left behind the life of a farmer and became a student of the Assenzi, a race of scholars. Among them, he learned the history of his race and of how Man the Cruel destroyed the world before disappearing into the mists of time and legend.Or have they disappeared..?

Thru Gillo has proven his courage in battle against the invading forces of Man the Cruel. But when he falls into the hands of the enemy and is taken to the distant land of Shast, he will be forced to trust a most unlikely ally -- a human woman....

As the battle continues, Thru Gillo has ever-harder work cut out for him. For one, the land wars have moved to sea. For another, the hero will have to choose from the three females who lay claim to his heart. But first he'll have to survive the iron-fisted clutch of Man the Cruel...