Altered Tides. The Galactic Captains, #5

A malfunctioning STAR drive strands Captain Ales in a new galaxy. Trapped on a dry, dusty red moon where the rains fall only once every forty years, the restless population barely survives on a teardrop ration of water. Now, the rains are years overdue, and the ruling clerics view Ales as a savior-or a devil. Just as Ales and the She-King's brother discover a secret the clerics have been hiding for far too long, this world is invaded and torn apart from a most unlikely source. The blue moon is a world covered in water-water that flows over to the red moon as rain every forty years, thereby drying up the domain of King Sarlord.
He's finally had enough and gathers an army to sail into the sky on the waterspout, land on the red moon, and defeat the god who steals his ocean. His son, Prince Malar, will do anything to avoid staying behind, but even he gets much more than he bargained for when the world as he knows it is swept away on altered tides.